Problems with OBS video software - can anyone help?

I've recently been having awful trouble with OBS - it is so severe I cannot use it at all, the video and the audio are completely out of sync, however much I move them around. This happens somewhat when I make an ordinary, straight to camera video but when I simultaneously try to record the screen at the side, the lagging is extreme.

I've tried all the fixes I found on the web - nothing seems to help.
Mac Sonoma. I was using OBS 27 and when everything went weird (for no apparent reason, I hadn't changed anything), I upgraded to OBS 30.
Again, no difference.

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