Bug: Can't enter Copper Coronet after returning from WK (killed some of the monsters in Level 3)

I am in Chapter 2, and completed most of the major quests and the 2nd Level of Watcher's Keep. I have the recommended mods for BG2EE + Keeping Yoshimo installed, and after returning from Watcher's Keep (cleared some areas of Level 3) , I am suddenly unable to enter CC. my older savegame actually works, but I don't want to replay from the older savegame as WK Level 3 (especially the demons!) is very hard for my current party level.

Any suggestions?