Hi, not sure if you're aware of this issue, but it seems like after playing the game for a while(Local Game Master), the performance drops astronomically, to about 10FPS. It stays at about this range until restart, no matter the weather nor, the rendered area. Seems weird, as the game runs really fine, but then - This bug occurs, and kills the experience completely.
A thing to note is that the GPU utilisation seems really low when that occurs, which is, again, strange.
Hopefully you can get to the bottom of this, since it obviously isn't a performance issue - Rather seems like a plain bug.