GPU drops frames in VR with foveated rendering enabled

my gpu constantly drops frames every 15–30 seconds if i enable foveated rendering. this option lowers gpu latency from 5.5 ms to around 3–3.5 ms, but these frame drops are driving me crazy.

if i disable the option, i get super stable fps with no drops. you might say, “what’s the problem then?” and i’ll tell you - right now i'm driving the mx5 rookies series on old maps with just 12 cars. i haven’t tried it on recently remodeled maps (i think they’re more demanding), and there are plenty of series with way more cars. so i'd like to keep some performance headroom if possible. foveated rendering is basically free fps, since i don’t notice any drop in video quality.

do you have any ideas what it might be? i don't have any monitoring tools enabled besides fpsvr. the frame drops are on gpu only - no spikes on the cpu frametime graph.

my pc specs:
gpu: rtx 5090
cpu: 9950x3d
headset: psvr2 (90 hz)
ram: 64 gb