Shader flickering in old project, not new

I’ve got two 2022.3.14 projects running URP. I’ve imported a couple asset packages I want to use into my loading project to look at them, and then imported them into my real project to start using them, but in the real project the flicker black/white/normal with every frame. They work fine (on the right) in the newly created project. The “real” project (on the left, can see part of it flickering black in that frame, but all of the materials flicker on and off with every frame) has been continuously upgraded since Unity 2018, and was originally BRP.

I’ve gone through all the URP settings, and quality settings and things, but this happens even in the inspector preview of the prefabs. Again, there is no flickering in the freshly created project.

Any ideas what I can look at to try and fix this?