I'm trying to get the bottom of this really weird issue I've run into. When I have a multicam clip that is 4k loaded in the source monitor, playback in the timeline lags and starts to drop frames. This happens only when a 4k multicam clip is loaded in the source monitor. If I click out of the source monitor into another tab like Effect Controls the timeline plays smooth again. Interestingly, if I undock the source monitor the timeline plays smoothly. It is only when I have a frame of video loaded in the source monitor and the source monitor is docked into the interface does this happen.
I'm on Mac OS Big Sur 11.6.5. The issue happens in both Premiere 2021 and 2022. It happens across the 3 devices I edit on. Late 2013 Mac Pro 16 GB, 2019 Mac Pro 32 GB, and a 2019 Macbook Pro 32 GB.
The media is transcoded to Prores 422. I also generated ProRes Proxy files. Proxies are enabled.