Changing drawableSize also seems to somehow disable VSync (or whatever it's called on MacOS). For a very lightweight application, the time it takes for nextDrawable to return goes from ~6-7ms (120fps) to almost zero.

Thank you for the reply, but having regular 1-second stalls is still highly irregular - the delays are too large IMO to be considered a regular frame pacing issue. Do you have any hypotheses regarding why it might be happening? Are there any requirements to where drawableSize must be updated to avoid these stalls?