"Bad file" - TVPaint file corrupted

[humble.bumble]

Hi,
a project that Ive been working on has suddenly become corrupted. When I try to open it, TVP says its a "bad file" and then either crashes, or opens the project but there are always several layers missing. It was originally a bigger file (over 1 GB), but it became much smaller (like 300 MB) since the first "bad file" incident. This has never happened to me before. I have multiple backup files (stored on different USBs or PCs) and all of them are corrupted this way.
Ive attached a pic of what it looks like when I open the project versus what its supposed to look like (a frame that I exported before the file was corrupted).

Is there any way to recover the project?
Thanks in advance

[slowtiger]

This looks like just one layer is missing. Just a guess: is that background drawing a separate image file, and is it linked to the TVP file?

[Dean]

Hello, do you still have access to the multibackup files?
Also, was the project saved on a different driver from the one on which TVPaint was installed on?

[humble.bumble]

Hi, no sadly I dont have any multibackup files. Ive always copied just the project file onto my other drives to work on it from home etc (so Ive opened the file on multiple computers - however always in the same version of TVP).
Ive reloaded my bgr layout into the project (btw is it possible to unlink it from the original image file, so that the TVP file isnt dependent on it and the image data is stored in the TVP project itself?). All my character animation luckily seems to be there, but the layer with the red letters isnt there (well, the layer IS there but its empty) - as you can see in the screenshot, the bottom half of the letters disappeared, and when I opened the file today, the whole thing is gone.
Also Im very nervous about the fact that this project file is now three times smaller than the original file - even though most of my layers seem to be fine, thats kinda weird, isnt it? I definitely did not change the resolution size or any other stuff like that.

[Dean]

This is weird indeed, were all the computers using the exact same TVPaint 11 version?
If multibackup was enabled on any on the machines, there might be some backup files remaining in the folder where the project was saved.
They have a name similar to the project's but a different extension and can be opened like a normal project file.