Logic Pro X playback stutter on brand new Mac Studio M4 - Sequoia 15.4.1

I'm having playback stuttering in Logic Pro on a new Mac Studio I've just set up. I didn't have this problem on my 2019 iMac I upgraded from.

The playback will stutter or restart if I have the cycle bar on and sometimes stutter at restart. Someone posted a solution about MIDI inputs and I've turned those off as I'm not using any external MIDI device, just a USB recording interface for input and sound output, so this didn't make any difference to the problem. I've spent a lot of money here and I'm already wishing I hadn't bothered!

It will not play through an entire song without stuttering which is useless if I'm recording.

Advice please. This is ridiculous.