For future reference (I had a similar problem), disabling ‘Generate Mesh Distance Fields’ in project settings worked for me.
Adding some info, I recently noticed this happening in UE5.2 with emissive materials, possibly depending on how strong the color input for the emission pin on the shader is. Haven’t tested if this is related to that option, or a problem on its own, but non emissive objects didn’t do it.
Yes! That’s exactly what it was for me.