The mini map in the BF is bugged yes.
As for your dungeon being empty, there is a
Patch to fix that.
If you refer to your dungeon not being empty of monsters, but nothing on the 3rd level, the BF gets randomly generated when you enter it the first time, so not everyone's quest monsters are found in the same dungeon, some get all of them in the first one, other find them spred out between 1-2-3, others find them all in the last dungeon.
