[Bug] Can't finish Tali's Loyalty Mission

[Cluisanna]

ETA: I fixed it by verifying the integrity of the game cache.

I decided to go back and do another replay of the Mass Effect series from start to finish.

Everything went well until I got to the Tali:Treason quest (obviously, spoilers!). At first I got the bug where talking to Raan initiates the "You set me up!" conversation; I restarted the mission and went in again, let the normal conversation trigger and proceeded to the Alarei. During the trial as well as while talking to the admirals I noticed the camera bugging out a lot, just focusing on walls or other people instead of those talking; there were also often some weird pauses before the conservation options for Shepard appeared.

I then went through the Alarei, picked everything up, and returned back to the Rayya. Once there, the admirals were talking about Tali having been killed, like normal, yet I noticed their voices coming from the wrong direction. When I entered the garden plaza, their conversation stopped as it would normally do because of the cutscene being triggered - but nothing happened! The plaza was completely empty, and I could just walk around it with no conversation or cutscene triggering.

I tried going back to the shuttle, and the voice file of the admirals talking about Tali being KiA triggered again, but the plaza was still empty. Going back to the Normandy wasn't possible either, and the people in that area still made comments as if I hadn't been to the Alarei already. I tried loading the autosave from before the fight with the Geth Prime several times, chosing different conversation options, waiting for the admiral's voice file to completely play, cutting it as short as possible, etc. etc.

I restarted the game and loaded from the last autosave, but the bug was still there. I then restarted the game once more and did the whole mission again (with the "Restart Mission" save file), but the bug is still there.

I can't think of anything else to do - this is very frustrating, since I don't want to lose Tali in the Suicide Mission (and can't even leave the Rayya anyway without loading a save game from yesterday). This has never happened before in my at least six playthroughs. I did have to delete the game some time ago and this is the first time playing with this new installation, but I just downloaded it through Steam like always.

Has anyone else had this problem? Any idea what to do?

ETA: I just started again from my save file from yesterday and did the whole Treason mission again. The bug was still there. I am officially out of options right now. Any help in fixing this or somehow making Tali loyal without completing her mission would be appreciated.