Hi there, this seems like a rather bad bug so I figured I would post this here and maybe get some help on the matter.
Some materials have started to brake in my project and can no longer be applied to any objects in the scene, regardless of that, the materials will continue working on any object that had the material already applied to it.
Restarting does not fix the issue, neither does recompiling the materials in question.
The bug occurs with brushes aswell as static meshes.
I do not have any repro steps since, one moment it worked, and in the next moment I couldnt apply the materials anymore.
Perhabs the issue is more with the meshes rather than the material. Since the material doesnt seem to work with new meshes in the scene. Displaying the default checkerboard material instead.
This is weird
In order to assist you I am going to need some steps to reproduce this issue on my end in a blank project, as well as some screenshots so I can visualize the issue you are reporting.
I am assuming by brush meshes you are referring to the Geometry tab where you can create additive and subtractive meshes?
Let me know if you have further questions or need additional assistance.