1) There's an invulnerable Romulan Centurian Scientist on the surface. My sniper rifle could knock her down, but my shots did no damage. Fortunately her attention was on three equally unkillable Remans, so I could ignore her.
2) This isn't really a bug, but just something clumsy. It occurs at the panel where I queue the power drain for the force fields. On the rooftop of an adjacent building is a fighter, and a team of Romulans who beam in after you activate the panel. Apparently the mission has been changed, and now an orbital strike or something kills them instead of my doing it. The problem is that a dialog box opens right after I activate the power drain. It blocks my view of the Romulans beaming in, and of what happens to them. There's the sound of an explosion, then when I get the dialog box out of the way I see a bunch of bodies. If i hadn't played the mission before I wouldn't know what occured.
3) In the fight with Hakeev: I get the cutscene where Obisek beams down, then I immediately jump to a second cutscene where Obisek kills Hakeev. I imagine there should be a fight between the two.
4) In the final space battle, the Leahval's shields appear to stay at 100% until the ship is disabled. I don't think its shields are actually undamageable, since the fight wasn't that hard. It would have taken much longer if I was depending on shield bleedthrough and DoT effects to disable it.