Audio recording crackling in Logic Pro, but not GarageBand

Logic Pro has been working fine for years, but suddenly recording any audio recording sounds like it is underwater, crackly and barely making it through. However if I try any other DAW, it works just fine, so definitely not an interface issue with my SSL2+ or the connections, but a settings or software issue in Logic Pro. You can see I'm working on something below and have created a new track called "Audio is bug*ered" - the wave form shown is for a single open strum on the guitar but only intermittent audio is being recorded.

Last thing I tried to do before it all went to the wall was record a midi track from a M-Audio Keystation Pro 88.

On a MB Pro M1 with 32Gb Memory on OS 14.1.2, and Logic is up to date. Have tried many things, same result just using built in audio, in new projects, deleting plist, resetting logic settings, even deleting the app and reinstalling.

Anyone who can help me not go insane just before Christmas will definitely be on Santa's good list...