Setting the codec to VP9 will cause the camera track to show at ~2fps for remote users. The WebRTC stats show the Scalability mode to be L1T3 which is to my knowledge not what the default is supposed to be, as is the case at meet.livekit.io (L3T3).
Screen share is not affected as I am aware it uses the contentHint: "motion" property value.
This issue is mostly evident on Chromium browsers, so far unable to reproduce on Mac Safari