still no fix for this problem, even with the latest version of the game - I'm in a different, but similar situation. 2019 16" MacBook Pro - Intel (built-in display capped at 60hz) - Both of my external monitors refresh rates are cut in half when sims 4 is in full screen mode. My 60hz TV switches to 30hz in full-screen and my 120hz external monitor switches to 60hz in full-screen. Manually changing the refresh rate to the display's highest option from apple's settings automatically exits sims from full-screen and puts it in windowed mode. Pretty frustrating, actually. I have been able to get this working by 'mirroring' my external display with my MacBook and slamming my face against the keyboard about 3 or 4 times. But, I'd prefer to not go through all of that hassle when playing the sims.
