Gizmos menu - classes missing, others being ignored

In one of my projects, in Unity 2020.3.0f1 on Windows 10, about half of the “Built-in Components” are missing from the Gizmos drop down in the scene view. They’re not just in the wrong place, as they aren’t showing up in the “Scripts” list either.

Separately, I have a script which toggles Collider Gizmos on and off. This has also stopped working. I have tried restarting Unity with that functionality removed, and it makes no difference to observed behaviour.

The “Gizmos” menu seems to be misbehaving in general. In a scene with Light components visible there are Light gizmos showing. Toggleing Gizmos → Built-in Components → Light doesn’t hide them, and nor does toggling “Built-in Components” as a whole.

If I open an empty project I get a full Gizmos list in the same version of Unity.

Has anyone else experienced anything similar? It’d be nice to narrow down the potential cause.

Yep we are seeing the same problem in our project