Testing the September 26th SVN on Windows XP, Game: Goblins Quest 3 CD (DOS/English).
In the screen with Queen Xina, for some reason after obtaining the axe Fulbert will no longer climb the thing to knock the skull over. He will be able to the first time you enter the room, but any time after that, no dice.
demonstration of the bug
Raising priority. This is a release-critical bug.
I also encountered this bug. However, it was only temporary and went after a while in my case.
It seems to be the same than bug #2355116, which is referenced in the wiki as a script bug.
Script bug already referenced https://sourceforge.net/tracker/index.php?func=detail&aid=2355116&group_id=37116&atid=418820 as previously mentionned.