Hi!
I’ve been dealing with quite an issue lately. I hope you can help 
I am using Rhino 6 in conjunction with V-ray Next. My mesh quality was set to Jagged and faster until now. I’ve mapped allmy objects with v-ray materials and right before final rendering I wanted to change the mesh quality to Smooth and slower. Once I’ve clicked onto the “Mesh” button in the “Properties” charter, most of the objects in my Render view mode turned white - into the defaul material. All my materials are gone and there is no way renewing them with ctrl+z or so… (luckily I had a backup). The materials still extist in the v-ray charter, but they are no longer assigned to the the objects/surfaces. This must be some kind of a bug, right? 
I would be really grateful if someone could explain me what is going on…
Thanks a lot
Chris