Fluctuations from 60 fps

I am at my wits ends, having googled, red tons of reddit threads, and the issue logs for Apollo/sunshine/moonlight etc.

I've setup a virtual monitor that syncs with client requested refresh rate via moonlight, so I know they are not different - both are 60hz (not one 59,94hz which could cause issues). Vsync, I've tried all different combos I can think of.

No matter what I do, I get occasional fluctuations from 60, down to 59 and up to 61. It's more infrequent since I setup the virtual monitor, but it still happens intermittently.

Hardware isnt bottlenecking, I am on a fairly ok card, a 5070. Resolution doesn't change the behaviour either, fluctuations remain.

Any ideas?