Doorkeeper Žák in Sazava, relic quest bug

There’s sidequest to bring him relic, which i did like 10 to 15 hours before i got to “trebuchet” quest.
Back in time i decided not to return the relic and now when i talk to him, he calls me a thief and my game gets stucked in loading screen (even after 2hrs of loading there was 0% progress).
When i try to return it to its place there appears to be “use” button, yet when i do it, nothing happens and it permanently disapears.

I actually tried to kill doorkeeper (just for testing purposes, this was not what i intended to do) and then see what happens. IDD there does not seem to be way to kill him without trebuchet q npc noticing it. I could not catch him up later then, yet i was able to catch another guy from that house to get again stucked in loading screen.

Just wondering if it’s possible to finish my current game or not.

Forgot to mention some important detail that it’s on steam version

Bump, killed doorkeeper outside, then NPC for trbuchet quest ran outside.
I was able to do the sidequest to get him outta monastery, but in meantime he went back to his house and now when i try to talk to him my game (after cutscene which is supposed to be played at our 1st meeting) gets stucked in infinte loading screen. At this point i can’t finish it without starting over again or loading 15hrs old save.
Please fix this quest asap