Sinister Enclave gives no XP for being accomplished, this really sucks!!!
When we took the quest, all Pcs had it in their journal, but I did not get a list of PCs who took the quest, assuming that it was just a minor bug, we continued the quest onward and finished it without many problems, none of them were bugs. However, we tried to turn in the quest, it said the quest was already finished by another party member.
None of our pcs finished the quest