Hey All 

MacOS 15.5 Capture 2024 Version 2024.0.46, M2 MAX 

Rendering Capture on an external display runs <1FPS when maximised (option +). When the window size is slightly dragged and changed, the render runs at full FPS.

Capture stats reports FPS is running at normal refresh rates at 100% quality (when visually rendering at <1FPS) 

When Full screen mode/ (cinema mode or what ever macos calls it now), it also renders fine.