IOS14 - Metal extremely slow in simulator

Hi,
I just upgraded to Xcode 12.0 .

Running an app which uses Metal in the iPhone XS simulator. Before upgrade, the app was running at 60 FPS. With the new version of Xcode, the app is running at 15 FPS. This also happens on the iPhone 11 simulator.
No problem on the actual iPhone XS device - runs smoothly at 60 FPS just like before.

Any ideas?