If you speak multiple times with Cunus Pompus about Zafirbel Bay Company in the same conversation, he keeps gifting flasks of Telvanni Bug Musk. He only changes the dialogue after you quit the conversation and restart it.
Willam Rilard keeps mentioning sarcastically that he's going to hear Bidsi Vidryon's petition shortly even after the quest is over and contraband was exposed.
During the Quest "Out of Order", Miremos is moved from his post at the top of the Drakelight Beacon (apparently to the Ashlands?) to make space for Tulnus. However, when he came back, he was dead. It doesn't seem that was supposed to happen.
I was told this was a bug and asked to report it. After encountering the guard of the vault in the ZBC company vault cell and fighting him, two additional NPCs have their fight set to 100. The dude in the room with the code book, and a nord mage in the entryway. According to Pralec "The bug is that when you get into combat with the guy guarding the vault, the other two guys will get their fight set to 100"
The issue is basically in the title; it is impossible to converse or otherwise interact with Saylenus. He just keeps repeating his voiced lines. Khazar appears to have brought the issue up on the Discord server back in October.
Brother Against Brother requires you to wait two days until the trial begins in Roa Dyr. If you go there before that time and talk to Llaren Ilvi, he will still have the trial dialogue. If you choose "Let me persuade him to repent" the journal will update and the two brothers and other needed characters will never be moved to the Hall of Judgement. This prevents the quest from being completed.
The dialogue for Llaren Ilvi should have the conditions changed so he will only have the topic after being moved inside the Hall of Judgement.
Durning Brazen maiden quest at the point when Tulnus asks you to break in the ship to find some dirt on the captain, if you deny his request you can speak with him about Brazen Maiden and deny his request again infinitely, and he pays 100 gold to you every time