I created a PBR material, and then made duplicates with different colors. That’s not the weird part. I decided to change the opacity of one of them to 60. It didn’t show any difference in the raytraced preview, so I set it back to 100, and it then became overly bright. The same thing happened when adjusting the opacity of the duplicates. I fixed the brightness by changing the material type to custom and then back to PBR.
I know about the issue, it is on my list to fix: RH-58065. A safer workaround for now is to just toggle the display to say wireframe, then back. That way you don’t lose any settings you have made to your material, in particular those settings that are not understood by the custom material.