Im not 100% sure if this is a bug or a feature. But in builds when some debug modes are changed for example (HDR) ones, the debug panel disappears.
Here in the video I switch between Gamut View, Gamut Clip and Values exceeding Paper White. They all work, but the panel/name is not visible, I might not know which one is which as a new user.
Repro:
1) Build any player in developer mode
2) Open debug panel and cycle through HDR modes.