I have almost the exact situation and I have a brand new RX 570, any drivers before 19.12 work fine, no flickering issues at all. But once I install 19.12 all seems well for about a day and then suddenly it starts having flickering issues. I think it may be caused after I let my PC sleep and then wake up after a few hours but I could be wrong. I don't have any driver crashing issues though, only the flickering. Unfortunately the only fix is to use an older version of the driver, for now at least. I sure hope they fix this problem because I'm really enjoying the new Radeon Setting application.
Edit: I believe the issue(for me) is actually caused by the Performance profiles, mind you I only use the manual tuning for a custom fan curve but I found out that once I hit the reset button at the top right of the Performance panel, everything started working fine again, no more flickering issues! Maybe give this a try and see if it works out for you as well. I attached an image for clarification.