Yeah, that's definitely some bottleneck there.
I'm having memory clock fluctuate wildly during certain games (e.g. RainbowSIX Siege), but not all of them (e.g. Battlefield 1 & 5). Since I don't mind the noise and know HBM memories are sensitive to temperatures, I've set very aggressive fan curves and maximized the power limit.
What could be the problem here..?