@misstuna Hi. First of all very sorry to hear you’re having issues. This is a problem that the Pencil2D team has been very involved in fixing after it was discovered.
I made a guide on how to 1) prevent this issue from affecting your work 2) attempt to partially recover the animation. Please read it carefully within the prevention guide there are links to the recovery guide as well.
Lastly, if you have any issue with the guides, please update this thread and i’ll gladly try to help you when I have some free time from work.
Edit: On a related note would you mind uploading your file to a cloud service of your choosing so the development team can review the file? We want to address this problem as much as possible as it’s been something that’s been creating discomfort among a few users ever since older versions and even though definite steps were taken to improve the issue, we have to yet still find the root cause it seems.
Edit 2 Sorry, also if possible can you copy the contents of that error message and paste it in a new comment on this thread? it’s important to help developers understand what has caused this.