Full screen black flashes on M1 iMac after recent update

Hi all!

After a recent update (within the last week) I’ve started to get fullscreen black flashes that correspond with large graphics updates, e.g. scrolling in Firefox, maximising Konsole, switching between windows, large amounts of Konsole output. They seem to be only a handful of frames but cover the whole display including the KDE menu bar etc.

I’m using KDE on Asahi Fedora 40 on an M1 iMac. The problem occurs with or without an ICC profile for the display configured.

Interestingly it seems to be random whether a given “boot” will have the black flashing problem. Rebooting a few times seems to fix it, and then rebooting again sometimes it’ll come back again.

Is this a known issue? Anytihng I can grab to help troubleshoot? I see nothing relevant in journalctl output or dmesg.

Edit: also to mention I’m running 200% scaling and have blur disabled in kwin to avoid graphical artefacts.