Converting Mandalf with blodd money doesn't end the level

I've reached the point where the game says that converting mandalf with blodd money ends the level.

I convert him but nothing happens. Then the imps dig the gold and he respawns at the dungeon heart.

This is an infinite loop. I convert him but he returns every time and the level won't finish.

Please fix this! I don't want to play the level 1 all over again!!