issue 2D displacement

[skulldoestalkfast]

Hi there, everytime I try to render a skin with 2D displacement to retain all the details of the map, Vr5 gives me a chaotic result as you can see in the "red" picture. As if the UVs were moved also .

The correct one is same skin test with "normal" mode active.
Any suggestions?

by the way, also sometimes: modifying the quality parameters , "view dependent" and Edge length result in a render with parts of the volume "cut of" as if a boolean op was active. very strange

Thanks
P

Vray5 cinema R23 pc windows10