I haven't had much time to figure this out, but I thought I'd mention it in case anyone else is running into it.
Seems like TIR starts off fine and then as time in mission increases, the TIR starts to get very jumpy, that is you turn to look at something and it takes time to decide you have turned your head and tries to catch up, so instead of a smooth panning motion, you get a series of stuttery jumps to your end position.
As more time goes on, the performance gets worse and worse until you turn your head and it takes a second or two to decide to change position. Leaving the game and going into the TIR control panel seems to fix it BUT it might just be leaving the game and having it start over may be what actually fixes it.
It acts like something is progressively degrading over time, the same way you would see a something like a memory leak working (not saying its a memory leak, just the progressiveness of the process is similar). Once the degradation passes a certain point it goes downhill very rapidly so that the distance between livable and totally useless is pretty quick.
It might also have to do with the number of A/C in the area, as that is when it tends to go completely to pieces. However it doesn't get better when the number of A/C is reduced again, once its bad, it stays bad.
