I do not have the "Behavior" package installed, which seems to have caused a similar issue, according to Google.
Any idea why this happens now and if I can do something on my end?
The 2 game objects it's referring to are basic 3D shapes, made with the Unity ProBuilder 6.0.8 (latest).
So no custom code from my side. It's generated by ProBuilder.
Do I have to wait for a ProBuilder update?