I encountered this issue in 5.4 and found the cause was that a material would somehow have tessellation enabled on its shader permutation when it shouldn’t. This would then fail to find a corresponding shader variant since the material didn’t have tessellation/displacement enabled. Since it should only load fixed materials in the function where the crash occurs I simply disabled tessellation on the shader permutation before it tries to find the shader (since it should never be on) and that seems to have fixed things.