The Drunken Lizard Pub

I did it several times now, with open and closed chests, but when I step on the plate nothing happens.
I would like to get the third easter egg, because I want to know what happens.

I'm using 10.5.5

After putting the items (ring, hammer, ash, apple) in the chests, the portculli does not open, by stepping on the plate.
I can see a poltergeist, but how to get through?

When I remove the .map-files everything goes fine. That's curious.

I've played the game as a fighter till the end.
Now I want to replay as a magic user and in certain places the game crashes, for instance in the Grimmhold Maintainance Level or when I want to go east from Western Tanglewood, where Grimmhold West is located or to the south of Northern Crakamir.
I'm ...