I recently got my Strix 5700 XT a few weeks ago and so far its been good, but I had that heatsink issue where the heatsink wouldn't make full contact with the PCB. After fixing that, I finally had proper temperatures.
I spent another few hours tweaking the card, trying various voltages and clock speeds and settled on 2200Mhz at 1275mV, with the memory overclocked to 1800Mhz. This is where I started having issues with some games, the memory would randomly drop in frequency, lowering my fps by a considerable amount before shooting back up again. I already tried leaving the memory at its stock frequency which didn't fix the problem either.
I've looked up the problem, and it seems like I'm the only one whose card decides it's smart to drop the memory speed to ~500mhz before shooting up to whatever I set it to - before lowering back down again. My games might run at 60fps as long as the memory decides to stay in 'performance mode.' But when this bug kicks in, my fps can drop to as low as 20 before going back up to 60 a few seconds later.
Heres a screenshot of my HW monitor, it might explain the issue better than I can.
From my eyes, it seems like the memory is 'power throttling' seeing how the memory power draw in one of the photos is all over the place. But I don't know any better considering this is my first AMD card in a while.