@kevinh - Your talk about Windows debugging info prompted me to dig around. I found this app error crash info via the Windows event viewer after my hold-down-ctrl-g test. Other than saying it happened inside Qt I'm not sure what else to make of this info.
Spoiler:
Code:
Version=1
EventType=APPCRASH
EventTime=132913003427981800
ReportType=2
Consent=1
UploadTime=132913003457918176
ReportStatus=268435456
ReportIdentifier=41627c8f-396a-4085-922a-0fe1e53c71de
IntegratorReportIdentifier=92e19824-abe0-4a0b-83c3-c35775b882b9
Wow64Host=34404
NsAppName=Sigil.exe
OriginalFilename=Sigil.exe
AppSessionGuid=0000a8f8-0001-0019-059a-4808ac33d801
TargetAppId=W:0006d9d0fa9ade2638f89a299a0521443a1700000904!000000043a52331817c373ab964a244844c295fa2e5b!Sigil.exe
TargetAppVer=2022//03//07:20:54:43!6272f6!Sigil.exe
BootId=4294967295
TargetAsId=114260
UserImpactVector=808452912
IsFatal=1
EtwNonCollectReason=1
Response.BucketId=0d62cbf8c55a1203f9090a5aa07e07c0
Response.BucketTable=4
Response.LegacyBucketId=1803984510094542784
Response.type=4
Sig[0].Name=Application Name
Sig[0].Value=Sigil.exe
Sig[1].Name=Application Version
Sig[1].Value=1.9.1.0
Sig[2].Name=Application Timestamp
Sig[2].Value=62267113
Sig[3].Name=Fault Module Name
Sig[3].Value=Qt5Gui.dll
Sig[4].Name=Fault Module Version
Sig[4].Value=5.12.9.0
Sig[5].Name=Fault Module Timestamp
Sig[5].Value=5ef7924e
Sig[6].Name=Exception Code
Sig[6].Value=c00000fd
Sig[7].Name=Exception Offset
Sig[7].Value=00000000003a5348
DynamicSig[1].Name=OS Version
DynamicSig[1].Value=10.0.19043.2.0.0.768.101
DynamicSig[2].Name=Locale ID
DynamicSig[2].Value=3081
DynamicSig[22].Name=Additional Information 1
DynamicSig[22].Value=9861
DynamicSig[23].Name=Additional Information 2
DynamicSig[23].Value=9861e578cc24a204ea4d9e4def4e96a2
DynamicSig[24].Name=Additional Information 3
DynamicSig[24].Value=96aa
DynamicSig[25].Name=Additional Information 4
DynamicSig[25].Value=96aa7e80daf82377e9eb98f90b31b9a1
UI[2]=C:\Program Files\Sigil\Sigil.exe
LoadedModule[0]=C:\Program Files\Sigil\Sigil.exe
LoadedModule[1]=C:\WINDOWS\SYSTEM32\ntdll.dll
LoadedModule[2]=C:\WINDOWS\System32\KERNEL32.DLL
LoadedModule[3]=C:\WINDOWS\System32\KERNELBASE.dll
LoadedModule[4]=C:\WINDOWS\System32\USER32.dll
LoadedModule[5]=C:\WINDOWS\System32\win32u.dll
LoadedModule[6]=C:\WINDOWS\System32\GDI32.dll
LoadedModule[7]=C:\Program Files\Sigil\Qt5WebEngineWidgets.dll
LoadedModule[8]=C:\WINDOWS\System32\gdi32full.dll
LoadedModule[9]=C:\WINDOWS\System32\msvcp_win.dll
LoadedModule[10]=C:\WINDOWS\System32\ucrtbase.dll
LoadedModule[11]=C:\WINDOWS\System32\SHELL32.dll
LoadedModule[12]=C:\Program Files\Sigil\Qt5Concurrent.dll
LoadedModule[13]=C:\Program Files\Sigil\python39.dll
LoadedModule[14]=C:\Program Files\Sigil\Qt5WinExtras.dll
LoadedModule[15]=C:\WINDOWS\System32\ole32.dll
LoadedModule[16]=C:\WINDOWS\System32\RPCRT4.dll
LoadedModule[17]=C:\WINDOWS\System32\combase.dll
LoadedModule[18]=C:\WINDOWS\System32\WS2_32.dll
LoadedModule[19]=C:\WINDOWS\System32\ADVAPI32.dll
LoadedModule[20]=C:\WINDOWS\System32\msvcrt.dll
LoadedModule[21]=C:\WINDOWS\System32\sechost.dll
LoadedModule[22]=C:\Program Files\Sigil\Qt5PrintSupport.dll
LoadedModule[23]=C:\WINDOWS\System32\COMDLG32.dll
LoadedModule[24]=C:\WINDOWS\System32\shcore.dll
LoadedModule[25]=C:\WINDOWS\System32\SHLWAPI.dll
LoadedModule[26]=C:\Program Files\Sigil\Qt5Widgets.dll
LoadedModule[27]=C:\Program Files\Sigil\Qt5Gui.dll
LoadedModule[28]=C:\Program Files\Sigil\Qt5Core.dll
LoadedModule[29]=C:\WINDOWS\SYSTEM32\MSVCP140.dll
LoadedModule[30]=C:\WINDOWS\SYSTEM32\VCRUNTIME140.dll
LoadedModule[31]=C:\Program Files\Sigil\hunspell.dll
LoadedModule[32]=C:\Program Files\Sigil\Qt5Quick.dll
LoadedModule[33]=C:\Program Files\Sigil\sigilgumbo.dll
LoadedModule[34]=C:\Program Files\Sigil\Qt5Network.dll
LoadedModule[35]=C:\WINDOWS\System32\CRYPT32.dll
LoadedModule[36]=C:\Program Files\Sigil\Qt5QuickWidgets.dll
LoadedModule[37]=C:\WINDOWS\SYSTEM32\VERSION.dll
LoadedModule[38]=C:\WINDOWS\SYSTEM32\dwmapi.dll
LoadedModule[39]=C:\WINDOWS\SYSTEM32\WINSPOOL.DRV
LoadedModule[40]=C:\WINDOWS\WinSxS\amd64_microsoft.windows.common-controls_6595b64144ccf1df_5.82.19041.1110_none_792d1c772443f647\COMCTL32.dll
LoadedModule[41]=C:\WINDOWS\SYSTEM32\UxTheme.dll
LoadedModule[42]=C:\WINDOWS\SYSTEM32\MPR.dll
LoadedModule[43]=C:\WINDOWS\SYSTEM32\NETAPI32.dll
LoadedModule[44]=C:\WINDOWS\SYSTEM32\USERENV.dll
LoadedModule[45]=C:\WINDOWS\SYSTEM32\WINMM.dll
LoadedModule[46]=C:\WINDOWS\SYSTEM32\VCRUNTIME140_1.dll
LoadedModule[47]=C:\Program Files\Sigil\Qt5Qml.dll
LoadedModule[48]=C:\WINDOWS\SYSTEM32\DNSAPI.dll
LoadedModule[49]=C:\WINDOWS\SYSTEM32\IPHLPAPI.DLL
LoadedModule[50]=C:\WINDOWS\SYSTEM32\SRVCLI.DLL
LoadedModule[51]=C:\WINDOWS\SYSTEM32\NETUTILS.DLL
LoadedModule[52]=C:\WINDOWS\SYSTEM32\CRYPTBASE.DLL
LoadedModule[53]=C:\Program Files\Sigil\Qt5WebEngineCore.dll
LoadedModule[54]=C:\WINDOWS\System32\OLEAUT32.dll
LoadedModule[55]=C:\WINDOWS\System32\PSAPI.DLL
LoadedModule[56]=C:\Program Files\Sigil\Qt5WebChannel.dll
LoadedModule[57]=C:\WINDOWS\SYSTEM32\dbghelp.dll
LoadedModule[58]=C:\Program Files\Sigil\Qt5Positioning.dll
LoadedModule[59]=C:\WINDOWS\SYSTEM32\USP10.dll
LoadedModule[60]=C:\WINDOWS\SYSTEM32\dhcpcsvc.DLL
LoadedModule[61]=C:\WINDOWS\SYSTEM32\ncrypt.dll
LoadedModule[62]=C:\WINDOWS\SYSTEM32\urlmon.dll
LoadedModule[63]=C:\WINDOWS\SYSTEM32\WINHTTP.dll
LoadedModule[64]=C:\WINDOWS\SYSTEM32\DWrite.dll
LoadedModule[65]=C:\WINDOWS\SYSTEM32\Secur32.dll
LoadedModule[66]=C:\WINDOWS\SYSTEM32\msdmo.dll
LoadedModule[67]=C:\WINDOWS\SYSTEM32\dxgi.dll
LoadedModule[68]=C:\WINDOWS\SYSTEM32\d3d11.dll
LoadedModule[69]=C:\WINDOWS\SYSTEM32\d3d9.dll
LoadedModule[70]=C:\WINDOWS\SYSTEM32\iertutil.dll
LoadedModule[71]=C:\WINDOWS\SYSTEM32\kernel.appcore.dll
LoadedModule[72]=C:\WINDOWS\SYSTEM32\HID.DLL
LoadedModule[73]=C:\WINDOWS\SYSTEM32\windows.storage.dll
LoadedModule[74]=C:\WINDOWS\SYSTEM32\dxva2.dll
LoadedModule[75]=C:\WINDOWS\SYSTEM32\Wldp.dll
LoadedModule[76]=C:\WINDOWS\SYSTEM32\SSPICLI.DLL
LoadedModule[77]=C:\WINDOWS\System32\IMM32.DLL
LoadedModule[78]=C:\WINDOWS\System32\NSI.dll
LoadedModule[79]=C:\WINDOWS\SYSTEM32\NTASN1.dll
LoadedModule[80]=C:\WINDOWS\System32\bcryptPrimitives.dll
LoadedModule[81]=C:\Program Files\Sigil\platforms\qwindows.dll
LoadedModule[82]=C:\WINDOWS\SYSTEM32\WTSAPI32.dll
LoadedModule[83]=C:\Program Files (x86)\Sizer\hook64.dll
LoadedModule[84]=C:\WINDOWS\SYSTEM32\profapi.dll
LoadedModule[85]=C:\WINDOWS\System32\bcrypt.dll
LoadedModule[86]=C:\WINDOWS\SYSTEM32\opengl32.dll
LoadedModule[87]=C:\WINDOWS\SYSTEM32\GLU32.dll
LoadedModule[88]=C:\WINDOWS\System32\MSCTF.dll
LoadedModule[89]=C:\WINDOWS\System32\clbcatq.dll
LoadedModule[90]=C:\Windows\System32\AppXDeploymentClient.dll
LoadedModule[91]=C:\WINDOWS\SYSTEM32\ig8icd64.dll
LoadedModule[92]=C:\WINDOWS\SYSTEM32\igdusc64.dll
LoadedModule[93]=C:\WINDOWS\SYSTEM32\dxcore.dll
LoadedModule[94]=C:\WINDOWS\System32\cfgmgr32.dll
LoadedModule[95]=C:\WINDOWS\SYSTEM32\powrprof.dll
LoadedModule[96]=C:\WINDOWS\SYSTEM32\UMPDC.dll
LoadedModule[97]=C:\Program Files\Sigil\styles\qwindowsvistastyle.dll
LoadedModule[98]=C:\WINDOWS\SYSTEM32\CRYPTSP.dll
LoadedModule[99]=C:\WINDOWS\system32\rsaenh.dll
LoadedModule[100]=C:\WINDOWS\system32\NLAapi.dll
LoadedModule[101]=C:\WINDOWS\SYSTEM32\dhcpcsvc6.DLL
LoadedModule[102]=C:\WINDOWS\SYSTEM32\mscms.dll
LoadedModule[103]=C:\WINDOWS\SYSTEM32\ColorAdapterClient.dll
LoadedModule[104]=C:\WINDOWS\SYSTEM32\icm32.dll
LoadedModule[105]=C:\WINDOWS\system32\audioses.dll
LoadedModule[106]=C:\WINDOWS\system32\MMDevAPI.DLL
LoadedModule[107]=C:\WINDOWS\system32\DEVOBJ.dll
LoadedModule[108]=C:\WINDOWS\System32\SETUPAPI.dll
LoadedModule[109]=C:\WINDOWS\System32\WINTRUST.dll
LoadedModule[110]=C:\WINDOWS\SYSTEM32\MSASN1.dll
LoadedModule[111]=C:\WINDOWS\system32\mf.dll
LoadedModule[112]=C:\WINDOWS\system32\mfplat.dll
LoadedModule[113]=C:\WINDOWS\system32\RTWorkQ.DLL
LoadedModule[114]=C:\WINDOWS\system32\mfreadwrite.dll
LoadedModule[115]=C:\WINDOWS\system32\MFCaptureEngine.dll
LoadedModule[116]=C:\Windows\System32\mfh264enc.dll
LoadedModule[117]=C:\WINDOWS\system32\CompPkgSup.DLL
LoadedModule[118]=C:\Windows\System32\Windows.Media.dll
LoadedModule[119]=C:\Windows\System32\Windows.ApplicationModel.dll
LoadedModule[120]=C:\Windows\System32\twinapi.appcore.dll
LoadedModule[121]=C:\Program Files\Sigil\python3.DLL
LoadedModule[122]=C:\Program Files\Sigil\DLLs\_socket.pyd
LoadedModule[123]=C:\Program Files\Sigil\DLLs\select.pyd
LoadedModule[124]=C:\Program Files\Sigil\DLLs\unicodedata.pyd
LoadedModule[125]=C:\WINDOWS\system32\mswsock.dll
LoadedModule[126]=C:\Program Files\Sigil\DLLs\_hashlib.pyd
LoadedModule[127]=C:\Program Files\Sigil\DLLs\libcrypto-1_1.dll
LoadedModule[128]=C:\Program Files\Sigil\DLLs\_ssl.pyd
LoadedModule[129]=C:\Program Files\Sigil\DLLs\libssl-1_1.dll
LoadedModule[130]=C:\Program Files\Sigil\DLLs\_bz2.pyd
LoadedModule[131]=C:\Program Files\Sigil\DLLs\_lzma.pyd
LoadedModule[132]=C:\Windows\System32\rasadhlp.dll
LoadedModule[133]=C:\WINDOWS\System32\fwpuclnt.dll
LoadedModule[134]=C:\Program Files\Sigil\iconengines\qsvgicon.dll
LoadedModule[135]=C:\Program Files\Sigil\Qt5Svg.dll
LoadedModule[136]=C:\Program Files\Sigil\imageformats\qsvg.dll
LoadedModule[137]=C:\Windows\System32\appresolver.dll
LoadedModule[138]=C:\Windows\System32\Bcp47Langs.dll
LoadedModule[139]=C:\Windows\System32\SLC.dll
LoadedModule[140]=C:\Windows\System32\sppc.dll
LoadedModule[141]=C:\WINDOWS\system32\propsys.dll
LoadedModule[142]=C:\WINDOWS\System32\coml2.dll
LoadedModule[143]=C:\WINDOWS\SYSTEM32\LINKINFO.dll
LoadedModule[144]=C:\WINDOWS\SYSTEM32\ntmarta.dll
LoadedModule[145]=C:\Windows\System32\TaskFlowDataEngine.dll
LoadedModule[146]=C:\WINDOWS\SYSTEM32\wintypes.dll
LoadedModule[147]=C:\Windows\System32\cdp.dll
LoadedModule[148]=C:\Windows\System32\dsreg.dll
LoadedModule[149]=C:\Windows\System32\msvcp110_win.dll
LoadedModule[150]=C:\Windows\System32\OneCoreCommonProxyStub.dll
LoadedModule[151]=C:\Program Files\Sigil\imageformats\qdds.dll
LoadedModule[152]=C:\Program Files\Sigil\imageformats\qgif.dll
LoadedModule[153]=C:\Program Files\Sigil\imageformats\qicns.dll
LoadedModule[154]=C:\Program Files\Sigil\imageformats\qico.dll
LoadedModule[155]=C:\Program Files\Sigil\imageformats\qjp2.dll
LoadedModule[156]=C:\WINDOWS\SYSTEM32\MSVCP120.dll
LoadedModule[157]=C:\WINDOWS\SYSTEM32\MSVCR120.dll
LoadedModule[158]=C:\Program Files\Sigil\imageformats\qjpeg.dll
LoadedModule[159]=C:\Program Files\Sigil\imageformats\qmng.dll
LoadedModule[160]=C:\Program Files\Sigil\imageformats\qtga.dll
LoadedModule[161]=C:\Program Files\Sigil\imageformats\qtiff.dll
LoadedModule[162]=C:\Program Files\Sigil\imageformats\qwbmp.dll
LoadedModule[163]=C:\Program Files\Sigil\imageformats\qwebp.dll
LoadedModule[164]=C:\WINDOWS\WinSxS\amd64_microsoft.windows.common-controls_6595b64144ccf1df_6.0.19041.1110_none_60b5254171f9507e\comctl32.dll
LoadedModule[165]=C:\WINDOWS\SYSTEM32\WindowsCodecs.dll
LoadedModule[166]=C:\Windows\System32\thumbcache.dll
LoadedModule[167]=C:\WINDOWS\SYSTEM32\policymanager.dll
LoadedModule[168]=C:\Program Files\Sigil\DLLs\_elementtree.pyd
LoadedModule[169]=C:\Program Files\Sigil\DLLs\pyexpat.pyd
LoadedModule[170]=C:\Program Files\Sigil\Lib\site-packages\lxml\etree.cp39-win_amd64.pyd
LoadedModule[171]=C:\Program Files\Sigil\Lib\site-packages\lxml\_elementpath.cp39-win_amd64.pyd
LoadedModule[172]=C:\WINDOWS\SYSTEM32\edputil.dll
LoadedModule[173]=C:\WINDOWS\system32\dataexchange.dll
LoadedModule[174]=C:\WINDOWS\system32\dcomp.dll
LoadedModule[175]=C:\WINDOWS\SYSTEM32\textinputframework.dll
LoadedModule[176]=C:\WINDOWS\System32\CoreUIComponents.dll
LoadedModule[177]=C:\WINDOWS\System32\CoreMessaging.dll
LoadedModule[178]=C:\WINDOWS\SYSTEM32\igd10iumd64.dll
LoadedModule[179]=C:\WINDOWS\SYSTEM32\apphelp.dll
LoadedModule[180]=C:\Program Files\Google\Drive File Stream\55.0.3.0\drivefsext.dll
LoadedModule[181]=C:\WINDOWS\SYSTEM32\d2d1.dll
LoadedModule[182]=C:\WINDOWS\SYSTEM32\WININET.dll
LoadedModule[183]=C:\WINDOWS\WinSxS\amd64_microsoft.windows.gdiplus_6595b64144ccf1df_1.1.19041.1348_none_91a2627ccc89e3fb\gdiplus.dll
LoadedModule[184]=C:\Windows\System32\OneCoreUAPCommonProxyStub.dll
LoadedModule[185]=C:\Windows\System32\EhStorShell.dll
State[0].Key=Transport.DoneStage1
State[0].Value=1
OsInfo[0].Key=vermaj
OsInfo[0].Value=10
OsInfo[1].Key=vermin
OsInfo[1].Value=0
OsInfo[2].Key=verbld
OsInfo[2].Value=19043
OsInfo[3].Key=ubr
OsInfo[3].Value=1415
OsInfo[4].Key=versp
OsInfo[4].Value=0
OsInfo[5].Key=arch
OsInfo[5].Value=9
OsInfo[6].Key=lcid
OsInfo[6].Value=2057
OsInfo[7].Key=geoid
OsInfo[7].Value=12
OsInfo[8].Key=sku
OsInfo[8].Value=101
OsInfo[9].Key=domain
OsInfo[9].Value=0
OsInfo[10].Key=prodsuite
OsInfo[10].Value=768
OsInfo[11].Key=ntprodtype
OsInfo[11].Value=1
OsInfo[12].Key=platid
OsInfo[12].Value=10
OsInfo[13].Key=sr
OsInfo[13].Value=0
OsInfo[14].Key=tmsi
OsInfo[14].Value=221518937
OsInfo[15].Key=osinsty
OsInfo[15].Value=3
OsInfo[16].Key=iever
OsInfo[16].Value=11.789.19041.0-11.0.1000
OsInfo[17].Key=portos
OsInfo[17].Value=0
OsInfo[18].Key=ram
OsInfo[18].Value=16261
OsInfo[19].Key=svolsz
OsInfo[19].Value=237
OsInfo[20].Key=wimbt
OsInfo[20].Value=0
OsInfo[21].Key=blddt
OsInfo[21].Value=191206
OsInfo[22].Key=bldtm
OsInfo[22].Value=1406
OsInfo[23].Key=bldbrch
OsInfo[23].Value=vb_release
OsInfo[24].Key=bldchk
OsInfo[24].Value=0
OsInfo[25].Key=wpvermaj
OsInfo[25].Value=0
OsInfo[26].Key=wpvermin
OsInfo[26].Value=0
OsInfo[27].Key=wpbuildmaj
OsInfo[27].Value=0
OsInfo[28].Key=wpbuildmin
OsInfo[28].Value=0
OsInfo[29].Key=osver
OsInfo[29].Value=10.0.19041.1415.amd64fre.vb_release.191206-1406
OsInfo[30].Key=buildflightid
OsInfo[30].Value=52B26023-6AFB-4B98-A9BA-096039A02240.1
OsInfo[31].Key=edition
OsInfo[31].Value=Core
OsInfo[32].Key=ring
OsInfo[32].Value=Retail
OsInfo[33].Key=expid
OsInfo[33].Value=FX:117B9872,FX:1180989E,FX:119E26AD,FX:11A8C293,FX:11A8C2FE,FX:11C0E96C,FX:11C3F9D5,FX:11C6E5C2,FX:11C7EB6A,FX:11C9408A,FX:11C940DB,FX:11C96C7A,FX:11CB9A9F,FX:11CB9AC1,FX:11CC111C,FX:11D5BFCD,FX:11D898D7,FX:11DB147C,FX:1A92E6F
OsInfo[34].Key=fconid
OsInfo[35].Key=containerid
OsInfo[36].Key=containertype
OsInfo[37].Key=edu
OsInfo[37].Value=0
FriendlyEventName=Stopped working
ConsentKey=APPCRASH
AppName=Sigil is a multi-platform EPUB ebook editor
AppPath=C:\Program Files\Sigil\Sigil.exe
NsPartner=windows
NsGroup=windows8
ApplicationIdentity=1AAF5F10399A63B64D675C1AC2B6CDD3
MetadataHash=36998096
I'll also report any sort of crash in the future just for visibility that it happens.