"Oh no I'm sure I saved but the file is nowhere to be seen" can also be a result of user saving to AppData/Temp because that's where autosaves are being saved, and if you load an autosave, I think Krita later suggest this wild location to save the file as.

I can translate to Polish when you finish the English text.

That doesn't sound good: https://www.reddit.com/r/krita/comments/cxn349/krita_will_not_open_kra_file/ :( Will gather more information later (right now it's only the post), but I wanted to link it here before I forget.

Can you copy-paste the OpenGL Info section from help->show system information for bugreports

I added a link from my collection of links that mentions lldb and how to use it, I think I knew it from someone on IRC but can't say if the instruction is correct or not.

I added more explanation what I want from the explanation about tablet drivers.

re-opening Krita should offer to recover the autosave file

Anna Medonosová wrote:

(About the "Related" links about Dropbox issues and the workaround):

Anna Medonosová wrote:

I managed to reproduce it that way:
Open a big animation file.
Add a new layer on top of everything.
Add a new frame on 0th.
Draw something on it.
Wait for autosave to kick in and finish its work. (Save during autosave most probably won’t work, either, but it will leave the file unsaved, so Krita will ask whether we want to close it or not)
Save the file.
Very quickly click “X” on the window top bar; Windows ask if it should close Krita; don’t do anything
Krita will start responding and it will close just after that.
No saved file anywhere.
Not sure how reproduceable it is in general. Also there is that additional thing that Windows ask what to do with unresponding Krita - no one reported it beforehand.
I guess it happens when Krita is busy for example making a copy of the image and maybe that happens before Krita starts blocking itself because of the saving going on…