I have RX480 and i updated my drivers today to version 18.5.1 (clean install option) and something is wrong - i get fps drop with screen lag every ~1 second. Before driver update everything was fine, game ran smoothly on 120fps (cap). Switching to vsync "on" helps a little but not resolves problem. I dont know driver version prior to update but it was from something dated ~06/2017 and it worked well, now it is bad.
Game is Wolfenstein 2, here is video with statistics, look closely to lags as i move my screen around, also have a look on red spikes and fps drops on statistics in upper right corner.
I tried changing various game settings, i even went to "LOW" settings but it the same problem on low or high settings.
I also tried PUBG and Mass Effect 3, same thing happens so it is not game dependant.
GPU is not throttling, temperatures are fine, nothing beside driver update changed.