Jerky object resize

Could anyone help with this issue.

When I try to resize an object, while holding [shift] to contrain it's proportions, the object redraw jerks rapidly between big and small. This isn't something which used to happen, but happens all the time now - making accurate resizing impossible.

I'm using illustrator 28.5 on a MacPro, M2 Ultra with64gb of ram on Sonoma 14.3