this was back in version 0.66, a few months ago. I meant to ask back than but didnt I just waited for a few updates. how i beat the thief was definitely by "distracting him" using act and taking the bag while hes busy. I can try sharing the save files if that helps. I really dont know what happened. all i remember was turning in the bag, i did the quest twice with no issues third time did it in. i remember examining the bag to see read/open it but pretty sure it didnt let me. ( i consider this a freak accident)
https://drive.google.com/drive/folders/1FPY-3IJA23Xo52bhQDfnVfP5j1n62X-g?usp=dri...
Has it happened in other saves or if you have a newer build, in the new build? 0.66 was a while I go, I wonder if I've fixed that already in the newer builds and just forgot that the quest had a bug.
I think there was something about the quest that I had to look at when the guy who does the preset saves found something. I vaguely remember something like that, but I fixed it back then.
I just did a rerun of the quest and everything worked as they should have, hmmm....
I don't know, since I'm not sure what the thing that causes the problem is. If you can live without that one quest, I think there shouldn't be anything else that could break the save.
I asked permission to download the save file. I can try resetting the quest, but other than that, I don't know how to help.
https://mega.nz/file/DaRRER7L#0Tx75At_YSvnNcHbbt8xRS6cz6MAJFJcOsN7fBpCmYM
This should work. Not sure if it'll break again in 3 tries, but it works now at least.