You should be able to use a material instance for the surface particle material. I’ve tried it out, and it seems to work without any issues. Please make sure the material instance is the same in the particle renderer Material property as it is in the material remap list in the widget.
If you’re sure that everything is set up correctly and the issue still persists, please send me detailed repro steps / example project with the issue, and any details you can think of. Thanks.