As title says. The game starts fine, but after a while, at random, a tiny stutter will occur. It's just the tiniest of stuttering, but after that it's downhill from there, the stuttering becomes more and more abundant until it can't do anything else but stutter, severely dropping my fps in the meantime making the game unplayable. Frame times go all over the place, sound becomes choppy, the whole lot. In the past this would almost always lead to a driver crash but now it just keeps stuttering until I quit the game or it will stutter and driver crash anyway, though way less often (after which GPU is stuck at 100% load). Now I said at random, because it also sometimes works perfectly fine for an entire session, but usually it's doing what is described above. After a game (or game+driver) the game is fine again, until it starts stuttering again, this time almost certainly causing the GPU driver to crash.
Diving into the performance numbers with GPU-Z open yields to no obvious causes for this issue. GPU usage stays around the same 90% mark, so it's not that the game suddenly demands less from the GPU dropping clocks and causing these issues, but I've attached a log of GPU-z anyway of a session that led to a crash (the last 4 rows are usage after a crash, hence the 100% usage).
Ryzen 5 1600 @ 3.8GHz 1.25V
MSI reference Vega 56 @ stock core clocks and voltages, 900 MHz HBM, 0% power limit (do note this also happens at everything bone stock though)
16GB of DDR4-3000 @ 3000 16-18-18-38
ASRock AB350 Gaming ITX/ac
Corsair SF600 PSU
Windows 10 Pro 64bit 1709
AMD Driver 18.3.4
It's just PUBG, games like TF2, Doom, HL2, Portal are all fine.