When baking reflection probe with HDR enabled at 128 resolution the mipmap stops working in 2020.3.9. Changing the resolution to a lower value solves it. Higher value does not. New probe in same scene has same effect. Baking in other scenes works(!). EDIT: Ok so this only happens when there is a standard static cylinder or sphere in the scene, and the light has been baked. Changing the mesh to anything but cylinder or sphere solves it. I've never seen anything like it.