Strange jittering / performance headroom issue only with Airlink@120hz rtx3080

Hello, since i swapped 3060ti for 3080 (10G) I have strange performance issue with Airlink at 120Hz.

When my performance headroom gets under 50%, it stays stable for a few seconds and then starts oscillating infinitely and movement/image in the game becames jittery/stuttery and unplayable.  It usually jumps between 20% - 40%. Sometimes the frequency is slower. If you look at the sky and look back it will perhaps hold 41% but the oscillation never stops on it own.

It doesnt report dropped frames, Its not ASW or MSW. This affects every game. If headroom stays over 50%, its smooth. I think I have tried everything, including fresh install. PTC, resolution, bitrate, h264/h265, sliced encoding.. nothing changes. Never seen this with 3060ti.

90hz Airlink or Questlink 90/120hz doesnt do this. 

Maybe its hunting for V-sync offset? Overlay doesnt change though.