Tracked this down to latency query forwarding from playback appsrc to webrtc appsink.
Pull request: https://github.com/WebKit/WebKit/pull/13571
Committed 263794@main (ac78e4bede06): <https://commits.webkit.org/263794@main> Reviewed commits have been landed. Closing PR #13571 and removing active labels.
<rdar://problem/109035387>