Thanks for the tip, Tatubias!
But it is possible to keep rendering quality high AND avoid artifacts. Actually, Studio doesn't seem to properly understand shortcuts, only elements of shoutcut in main color get properly shaded. So the solution (apart from fixing Studio of course!!!) is to inline shotcuts (export from Studio to LDraw -> inline with LDCad -> open LDraw file in Studio)
But it is possible to keep rendering quality high AND avoid artifacts. Actually, Studio doesn't seem to properly understand shortcuts, only elements of shoutcut in main color get properly shaded. So the solution (apart from fixing Studio of course!!!) is to inline shotcuts (export from Studio to LDraw -> inline with LDCad -> open LDraw file in Studio)