is there some way / tool that could fix broken saves?

My original issue was I when I entered Lizardfolk village and few other location and saved my game, the save was corrupted and could not load (some JSON serialization error). In the end I did repair / verify / reinstall on GOG and the issue was gone. So I thought.

I was able to complete previously mentioned locations after that, but now when I try to enter Olegs I see very same error (it does not even load). I would not mind much, but my Nok-Noks quest just failed because I wasn't able to visit the location. The issue seems to be in save files, if I load my saves of other character (pre enhanced edition) I'm able to enter Olegs just fine.

Is there some way how to fix this? I don't really care about Nok-Nok and I can't give books to Bokken (don't mind about this quest much either), but I think one does need to visit the location for the Tasks for trio quest and this is quest I would like to finish.

P.S. I use no mods (only safe one with tons of portraits).