There was a bug in saving system mechanics which seems to be fixed now.
The fix might clear out your level progress which I'm really sorry about, but there was no other straightforward way of fixing it differently - hope you still enjoy playing Terry Poorflyer!
Best regards,
-- ł.
Update notes for 27 July patch
Source: Steam Community (opens in a new tab)
Build and release context
Steam update times within 24 hours of this post. Matching dates do not confirm which build it describes.
Build 9198019 · public branch
Steam updated · First observed