Yes, indeed Walther....they are freshly made in Infinite....and the .prv has nothing to do with it. It's not that they are not showing up in the browser..it's that they are actually gone...kaput...nixed...from the folder itself!! I can cook up 5 mats and put them in a folder....then I can copy and paste 5 more into the same folder from another one. As long as I access those mats through Windows Explorer, I can apply them to my object just fine. But when I turn that folder into a collection in the material browser...Vue deletes them from the folder itself....simply GONE!! Sometimes it's just half of them...other times it's everything in the folder....to the phantom zone!