Nope. Just received my Pimax a day ago and zero luck so far. Never expected this particular issue so didn't research specific incompatibilities between the Pimax drivers and AMD cards, but apparently it's a common problem. I have the exact same setup you do - 5700 XT and Pimax 5K +. Will have to return the Pimax, unfortunately, as the 5700 XT is beyond the Amazon return window and no way can I afford another new video card.
Anyone have a solution we don't know about yet?