Disabling webgl2 in the develop menu experimental features fixed the drop in FPS. However this is not a proper workaround for users. This needs to be fixed.

The problem still persists. Maybe got worse in 13.1. Safari Tech Preview is even worse! Do any of you have a good webgl 1 and 2 performance test we can try. I wonder if I adapt my tools to use webgl 2 I will get better performance.