There's never a crash, all motion just freezes on the screen. This issue did not occur while I was using a vega 56 and other components were the same as they are now, so I'm pretty sure it's because the video card is acting up. While running assassin's creed: odyssey with ultra settings, the freezing tends to occur within only a couple of minutes of gameplay, but it's less frequent while running metro: exodus. Yesterday I played about half an hour of it without any freezing while using high settings, but today it froze after about 20 minutes of running it on ultra settings. This issue does not seem to occur at all while running games that do not demand that much performance, such as dragon age: origins. My radeon software version is 19.7.5 and my operating system is windows 7.
Edit: After a few more hours of gameplay in metro: exodus, there has not been any other instances of freezing with that game, though there has been occasional very brief flickering and one instance of severe artifacting that did not occur again after rebooting the PC.
Edit 2: There was another freeze while running metro: exodus, so the freezing in that game seems to be several hours apart, while in assassin's creed: odyssey it still takes only a couple of minutes on average. Still no issues with games that have low performance requirements