Intermittent flicker (also in Qt Creator)

For some time, I've noticed that my app occasionally suffers rapid flicker. However it is intermittent and therefore hard to pin down. I have only seen it on my Mac (which I develop on), not on iPad or Windows (which I release on).

However I experienced it for the first time in Qt Creator too (10.0.2) which is of course built in Qt 6.4.3.

In Qt Creator, I had a collapsed section of code. Whenever I hovered the mouse over the arrow to expand it, the large grey overlay would flicker. I've attached a video to show where it happened, but unfortunately the video didn't capture the flicker itself. (Maybe that suggests the flicker is before or after some rendering step?)

In that instance it happened when Qt Creator was open in my external monitor.

For my own app, it happens occasionally with certain Qt Quick shapes flickering. I think this has happened on the built-in monitor, not just the external.

To get rid of it I've either restarted the app or shifted it to a different display.