Rollback of the progress in the file

Hi, I noticed an issue when Figma makes a rollback of saved updates in the file, i.e., I implemented some comments from the customer and in a day I saw that changes were not saved. At that time I didn’t have obvious indicators of unsaved changes/errors/connection issues/accidental undo-redo.
Later this issue was confirmed by my team mate for the same file.
What can be the possible issue? Thanks.