Open VRChat and load a reasonably complex world
Example: An old Neon Divide map that hasn't been updated in 2 years (This also occurs with more modern maps, but this map's performance is so bad it's a useful test case)
Stand somewhere in the map, and watch performance degrade sharply over a few minutes
This seems to be a CPU issue, CPU usage increases over time
On some hardware configurations, performance may jump back up again and then start degrading. Something to do with threads getting overloaded and new ones being spun up