The memory clock on my Vega 56 randomly gets stuck at the max value (800mhz stock) since a few driver versions ago. I think the problem started in 19.4.1. It was supposedly fixed in 19.5.1 according to the release notes but it wasn't. I'm currently on 19.6.1 and the bug is still there.
Seems to be a fairly random bug, as in sometimes it'll get stuck at max clock even while I'm doing nothing and the computer is completely idle, sometimes it'll fix itself eventually and go back down to the normal idle values, sometimes a restart is needed. I can't find any pattern to the bug.
My monitor setup is 1440p144Hz main + 1080p60Hz secondary monitor.