Viewing the Duplicati Server Logs About → Show log → Live → Verbose (or some other level) can sometimes see things retroactively, but I’m not sure how far it can go. It’s best used for new things.
log-file=<path> log-file-log-level=verbose is better if live log has nothing but you hope to catch next.
Process Monitor can also be set up to filter heavily, perhaps just on that one file and discard others.
Filter → Drop filtered events. Don’t let it grab too much or it might run system out of virtual memory.
Looking through event log around the times of the failed hibernate / standby or the restart might help.
I was thinking of Find Handle or DLL but that’s basically what Resource Monitor just did. There’s also a Handles view in the bottom half of the screen if you View → Show lower pane, but you’d have read File lines and ignore the ones that are program code (.dll). Sorting by Name (click) makes this a little easier.
There’s also a Threads view, but we’re not Windows wizards. Typically it doesn’t help, but you can look. What would be nice would be to attach a debugger to process, but that’s probably too far to go just now.
EDIT:
These are some sample lines at Verbose level, showing the source file scanning and the changes seen:
2023-12-07 20:04:09 -05 - [Verbose-Duplicati.Library.Main.Operation.Backup.FileEnumerationProcess-IncludingPath]: Including path as no filters matched: C:\PortableApps\Notepad++Portable\App\Notepad++64\backup\webpages.txt@2023-12-03_072112
2023-12-07 20:04:20 -05 - [Verbose-Duplicati.Library.Main.Operation.Backup.FileEnumerationProcess-IncludingPath]: Including path as no filters matched: C:\PortableApps\Notepad++Portable\App\Notepad++64\backup\webpages.txt@2023-12-03_072112
2023-12-07 20:04:20 -05 - [Verbose-Duplicati.Library.Main.Operation.Backup.FilePreFilterProcess.FileEntry-CheckFileForChanges]: Checking file for changes C:\PortableApps\Notepad++Portable\App\Notepad++64\backup\webpages.txt@2023-12-03_072112, new: False, timestamp changed: True, size changed: True, metadatachanged: True, 12/7/2023 9:25:30 PM vs 12/5/2023 8:27:17 PM
2023-12-07 20:04:26 -05 - [Verbose-Duplicati.Library.Main.Operation.Backup.FileBlockProcessor.FileEntry-ChangedFile]: File has changed C:\PortableApps\Notepad++Portable\App\Notepad++64\backup\webpages.txt@2023-12-03_072112
Yours somehow seems to have stopped scanning after that troublesome file (thinking based on math).
The reason I think it got at least to attempting to close that file was described above. Its code might be:
https://github.com/duplicati/duplicati/blob/master/Duplicati/Library/Main/Operation/Backup/ProgressHandler.cs could call that, e.g. on file close, but exact situation and code path are not known.
When situation gets a bit clearer, maybe some of the Duplicati developers can help look through code.