Were you guys ever able to find a solution to this?
I'm running Eyefinity, 5760x1080, with 50 FoV, and the right side mirrors will freeze and stop updating. They work if I pull back to a wider FoV like 70, but don't work at 50 FoV - possibly because they're at the edge of the screen, and the game thinks they're off the screen?
I noticed that if I turn on the right virtual mirror, than the main right side mirror will update along with it, and if I turn off the right virtual mirror than the right side mirror will freeze. The right small mirror is constantly frozen.
Edit:
I did more testing with a clean profile, and I found that I could reproduce the bug 100% of the time in an Iveco Stralis or Iveco Hi Way truck. The right side small mirror is constantly frozen when looking straight, and only updates if I look at it. The right side large mirror will update as long as I have the virtual mirror on, and will freeze unless I turn to look at it with the virtual mirror off.
Here's a screenshot of the right small mirror completely off while driving:
I tried a Volvo FH16 truck, and there the right side large mirror worked even with the virtual mirror off, but the right side small mirror was similarly frozen unless I turned to look at it.