Rhino 7 Mac Legacy rhino Renderer losing pbr materials links

Hi, Not sure if anyone is having the same problem as I am. Currently enjoying very much the Legacy Rhino renderer as its is very straight forward to use. But for some reason every time I import files from 3d warehouse, such as furniture and decorative elements, that come with pbr materials they show up in perfect condition. but if I close the file and reopen them a few days l later, some of the links get lost. Should I be saving the file in a different way? or is there an extra step to insert the materials of these object?

Rally need the help as it is the 3rd time that I relink materials and lose all the work.

Rhino legacy render does not support PBR materials. I’m surprised they work at all.

Why are you using legacy render as opposed to the current rhino render?

do these models render and save correctly if you render in regular rhino render?