Noticed a couple bugs int eh Merchant League quest line. When you go to the second floor and talk to Aldeth, he will tell you to talk to his captain of the guard. But, if after getting the evidence you talk to aldeth again, and you choose an option where he tells you to talk tot he captain, the captains dialogue is the same as the first time you talk to him again. Only if you talk to him a third time does he let you turn in the scrolls, and make all the dopplegangers appear hostile.
Additionally, if you try to go to the party with Aldeth, you will transition to be upstairs, but nothing happens. Your party and aldeth and the merchants just stand there and wait.
Also, the dopplelganger on the second floor, (Zortl?) just repeats the same dialogue conversation forever if you answer you know Dabron. In fact, it just cuts off. It seemed like he would say something afterward to end the dialogue, and then have some repeat phrase at subsequent conversation attempts, signifying you'd already spoken at least once.
The whole set of conversations and sequences of events on this quest seems bugged. I only found the one workaround if I spoke with aldeth once when he was on the second floor, then talked tot he guard captain, then got the evidence, then talked tot he guard captain again, then killed the dopplegangers. This is definitely immersion breaking, and ruined my attempt at playing through this through Aldeth only, not trusting anyone else in the League. You are forced to trust the captian, rendering the other branches of the dialogue trees with him useless.
I am playing legit, steam copy of vanilla BG:EE on a PC running windows 7 64 bit.