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Old 06-22-2026, 08:02 PM   #1
DragoLord19d
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a strange error

I'm getting a weird error when trying to open my epubs

calibre, version 9.9.0
ERROR: Loading book failed: Failed to open the book at C:\Users\Owner\OneDrive\Documents\Calibre\Silver Gambit\With Key in Hand (3037)\With Key in Hand - Silver Gambit.epub. Click "Show details" for more info.

Failed to convert book: C:\Users\Owner\OneDrive\Documents\Calibre\Silver Gambit\With Key in Hand (3037)\With Key in Hand - Silver Gambit.epub with error:
calibre_plugins.comicvine.utils:228: SyntaxWarning: "\d" is an invalid escape sequence. Such sequences will not work in the future. Did you mean "\\d"? A raw string is also an option.
calibre_plugins.comicvine.utils:228: SyntaxWarning: "\g" is an invalid escape sequence. Such sequences will not work in the future. Did you mean "\\g"? A raw string is also an option.
calibre_plugins.comicvine.utils:234: SyntaxWarning: "\s" is an invalid escape sequence. Such sequences will not work in the future. Did you mean "\\s"? A raw string is also an option.
calibre_plugins.fantastic_fiction.__init__:96: SyntaxWarning: "\." is an invalid escape sequence. Such sequences will not work in the future. Did you mean "\\."? A raw string is also an option.
calibre_plugins.fantastic_fiction_adults.__init__: 128: SyntaxWarning: "\." is an invalid escape sequence. Such sequences will not work in the future. Did you mean "\\."? A raw string is also an option.
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Old 06-22-2026, 10:07 PM   #2
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here is your problem:

Code:
Loading book failed: Failed to open the book at C:\Users\Owner\OneDrive\Documents\Calibre\Silver Gambit\With Key in Hand (3037)\With Key in Hand - Silver Gambit.epub.
https://manual.calibre-ebook.com/faq...rked-drive-nas

See for help:
https://www.mobileread.com/forums/sh...54&postcount=4

luck

bernie

Quote:
Originally Posted by DragoLord19d View Post
I'm getting a weird error when trying to open my epubs

calibre, version 9.9.0
ERROR: Loading book failed: Failed to open the book at C:\Users\Owner\OneDrive\Documents\Calibre\Silver Gambit\With Key in Hand (3037)\With Key in Hand - Silver Gambit.epub. Click "Show details" for more info.

Failed to convert book: C:\Users\Owner\OneDrive\Documents\Calibre\Silver Gambit\With Key in Hand (3037)\With Key in Hand - Silver Gambit.epub with error:
calibre_plugins.comicvine.utils:228: SyntaxWarning: "\d" is an invalid escape sequence. Such sequences will not work in the future. Did you mean "\\d"? A raw string is also an option.
calibre_plugins.comicvine.utils:228: SyntaxWarning: "\g" is an invalid escape sequence. Such sequences will not work in the future. Did you mean "\\g"? A raw string is also an option.
calibre_plugins.comicvine.utils:234: SyntaxWarning: "\s" is an invalid escape sequence. Such sequences will not work in the future. Did you mean "\\s"? A raw string is also an option.
calibre_plugins.fantastic_fiction.__init__:96: SyntaxWarning: "\." is an invalid escape sequence. Such sequences will not work in the future. Did you mean "\\."? A raw string is also an option.
calibre_plugins.fantastic_fiction_adults.__init__: 128: SyntaxWarning: "\." is an invalid escape sequence. Such sequences will not work in the future. Did you mean "\\."? A raw string is also an option.
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Old 06-23-2026, 10:29 AM   #3
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Get your calibre library out of the path of Onedrive.
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Old 06-24-2026, 11:01 AM   #4
lyfia
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Quote:
Originally Posted by gbm View Post
here is your problem:

Code:
Loading book failed: Failed to open the book at C:\Users\Owner\OneDrive\Documents\Calibre\Silver Gambit\With Key in Hand (3037)\With Key in Hand - Silver Gambit.epub.
https://manual.calibre-ebook.com/faq...rked-drive-nas

See for help:
https://www.mobileread.com/forums/sh...54&postcount=4

luck

bernie
I have the same bug even outside network drives:

Code:
calibre, version 9.9.0
calibre, version 9.9.0
ERROR: Loading book failed: Failed to open the book at D:\Downloads\A Life - Oxford University Press.epub. Click "Show details" for more info.

Failed to convert book: D:\Downloads\A Life - Oxford University Press.epub with error:
Originally the bug is exactly the same as in OP (same "comicvine", same problems with escape slashes), so I uninstalled the comicvine plugin , then the error message became blank --- what I pasted above. I've tried restarting calibre and Windows.
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Old 06-24-2026, 06:59 PM   #5
kovidgoyal
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That error indicates something on your machine is killing calibre worker processes, reboot in safe mode and see if it works.
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Old 06-25-2026, 06:36 PM   #6
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Quote:
Originally Posted by kovidgoyal View Post
That error indicates something on your machine is killing calibre worker processes, reboot in safe mode and see if it works.
I'd try but my computer crashes at any attempt to reboot into safe mode. That'll be another one for me to debug.

But I don't think it's caused by disrupted calibre worker processes because I can right-click and open other EPUBs within the same E-book viewer window, showing the same number of calibre worker processes in Task Manager when it succeeded or failed. I can't tell why some EPUBs work while others don't, but I know for a fact the failed EPUBs were still working two weeks ago. They are not corrupted files, and they can still be opened in other programs, including the calibre ebook editor (which didn't find notable errors with these files, by the way).
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Old 06-25-2026, 07:12 PM   #7
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Advice back up your libraries and config folder then run smart drive on your disk.

https://www.elevenforum.com/t/check-drive-health-and-smart-status-in-windows-11.8778/

If it passes smart drive then:

https://www.elevenforum.com/t/check-...ndows-11.8046/

bernie

bernie
Quote:
Originally Posted by lyfia View Post
I'd try but my computer crashes at any attempt to reboot into safe mode. That'll be another one for me to debug.

But I don't think it's caused by disrupted calibre worker processes because I can right-click and open other EPUBs within the same E-book viewer window, showing the same number of calibre worker processes in Task Manager when it succeeded or failed. I can't tell why some EPUBs work while others don't, but I know for a fact the failed EPUBs were still working two weeks ago. They are not corrupted files, and they can still be opened in other programs, including the calibre ebook editor (which didn't find notable errors with these files, by the way).

Last edited by gbm; 06-25-2026 at 07:14 PM.
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Old 06-26-2026, 07:44 AM   #8
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Thanks bernie, my disks passed all the checks. Other programs can open those EPUBs, so they are not corrupted. As for the crashes, I've recently upgraded my PC so it may be a driver issue, otherwise I suspect Windows update KB5094126.
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Old 06-26-2026, 08:02 AM   #9
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Quote:
Originally Posted by kovidgoyal View Post
That error indicates something on your machine is killing calibre worker processes, reboot in safe mode and see if it works.
Quote:
Originally Posted by lyfia View Post
I'd try but my computer crashes at any attempt to reboot into safe mode. That'll be another one for me to debug.
Quote:
Originally Posted by JSWolf View Post
I suggest you try rebooting in safe mode and then try calibre.
Why would you think they need instructions on how to boot to Safe Mode when they clearly already indicated their computer crashes whenever trying to reboot into Safe Mode?
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Old 06-26-2026, 10:11 AM   #10
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@lyfia what you need to di is a repair install. It's the only way to fix your computer without a full reinstall.

Go to Settings > System > Recovery > Fix Problems using Windows Update

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Old 06-26-2026, 02:58 PM   #11
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Thanks for the help but actually I've already done that. I've also ruled out recent Windows updates. It seems I'll have to do a full reinstall/reset to fix the drivers, but it's a bit off-topic.

Attached are 3 books that I've read in the past 2 months without problems with the calibre reader. I've even highlighted and taken notes. Only the Japanese book ("kimi no suizou") still works now. Perhaps you can tell the difference between what works and what doesn't.
Attached Files
File Type: epub Kimi no Suizou.epub (812.0 KB, 5 views)
File Type: epub A Room of One's Own - Virginia Woolf.epub (1.63 MB, 2 views)
File Type: epub GILGAMESH - Sophus Helle.epub (883.7 KB, 3 views)

Last edited by lyfia; 06-26-2026 at 03:01 PM.
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Old 06-26-2026, 03:06 PM   #12
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Originally Posted by lyfia View Post
Only the Japanese book ("kimi no suizou") still works now.
WAIT NO. The file I uploaded actually does not work. Strange but finally some development.

The original file still works (uploaded below). I copied it to another folder and renamed it (because the original has an ugly transliterated filename) for upload, the one I uploaded in the previous post, and now it can't be opened!!
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Old Yesterday, 10:52 AM   #13
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Guys I found the issue!! After disabling the plugin "ePub Extended Metadata {Reader}" everything's back to normal. The problematic plugin update is its latest on 2026-06-21.
Weird that calibre's Traceback couldn't catch this, though.
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