I can't turn in the "finding the culprit" quest until after the culprit confronts the MC. I looked in the guide and did all the things I needed to figure out the culprit, but I still can't turn the quest.
Hmm did you check Winston's desk and then submit the quest manually in the quest bar (click the turn in option?)
Was it an issue of the quest not turning up? You need to visit the library on day 3 or above, if you have the monarchy topic in your topics section then you need to check the desk after Keppler gives you the quest and never before
Did you check the desk prior the quest was given? In your inventory, is there a culprit icon? Looking at the code, I think the only reason the culprit item is not in your inventory is if you have checked the desk before the quest was given and you had the "Vampire Monarchy" topic at that time.
another fix is to talk to Winston at the sparring field after you have checked his desk, and the option to report him shud pop out
If that doesn’t happen, would you mind if I contact you via discord or the sort to try and test out a fix?