Jono,
someone else reported this issue earlier, and in their instance it was triggered by the default ICC profile supplied with a cintiq that for whatever reason caused rendering issues on mac os sonoma.
https://forums.artrage.com/showthrea...264#post543264 - here's the specific post with a fix for that;
if you don't use a cintiq, try plugging any .icc profile that is different from one supplied by apple or your screen manufacturer and see if it helps.
in this instance, I'm not sure if this should be fixed by apple, or by ambient design.