The command did work out in the way that my party was moved to the underdark but Jarlax got the same non sense dialogue as if he just joined your group when you appear in the snirvneblin village (now apparently drow village) for the first time. Unfortunately running change-log didnt list any mods
I've got the three fangs(only things lootable from the drakes apart scrolls of identification ^^) but when I talk to Jarlax he doesnt recognize them.
Probably because the dialogue where he explains the task of getting the dragon fangs never happened.
When you all three fangs
You should get the dialogue with this, unless the other bug really blocks everything.
Do you have the exact text that is displayed for proficency choice?