I’m seeing random performance spikes, where FPS will drop from 50 to around 10. Manipulators and MainThread will show 80+ms. This will continue for around 10-30 seconds, then FPS suddenly improves. This isn’t always back to full speed, there seems to be an intermediate state (for me it was 25-30 FPS). It will sometimes jump between the 3 states a few times (10-30 seconds each) until finally getting back to normal speed.
The switch between these states is sudden and obvious, both in the game and in the graph. One second everything is fine, the next you’re in slow motion, and it goes away just as quickly.
A similar thread got merged with some London performance issues. It’s unlikely that it’s the same issue. I’ve hit this in several places, including the middle of Kansas. It’s flat, there are no buildings, and the sim doesn’t model cornstalks, so I don’t think it’s terrain or object density.