Hmmm, that's strange I can't induce the fault now either
So what's changed since I did those tests last week - patch to Internet Explorer, MSE signature updates, and new versions of;
Free File Sync
Good Sync
Chrome
calibre-64bit
calibre-32bit
calibre-portable
Evernote
Word Web
Bow Pad
Clipboard Fusion
Ccleaner
Notepad++
Speccy
Nothing in the list leaps out at me. I keep a pretty tight ship regarding installs, apart from MSE signatures nothing gets installed automatically - everything is separately downloaded, installed and archived. I searched the Windows directory and found nothing new apart from that IE patch, today's MSE signature install, couple of icos, logs and prefetch files - but no new exe's or dlls.
I can't be sure I edited the same files, last week I just copied a couple of epubs into _Sandpit and then deleted them - no idea what they were?
Very strange.
BR