Model in Prefab materials gets updated(?) to Universal Render Pipeline/Lit when it shouldn't

Unity Engine
,
1

I have a project where we currently use Custom Shaders for everything.
In Unity 2021.2.13, all the material in the prefabs’ model are correctly imported with Custom/Lit, but in 2021.2.17 it gets imported with Universal Render Pipeline/Lit, and the ShaderGUI is greyed out.

Any ideas on what might be happening?

2

Reimporting All assets seems to fix it for me.