Logic Pro X playback pitch and timing messed up

In Logic Pro X, various tracks in my project suddenly have completely messed up pitch and timing after reloading - it is all a total mess.

One or two of the tracks are still on pitch and on time, but most are in various stages of slow and pitched down.

Admittedly it is quite a busy project with lots of tracks and various instances of things like Melodyne and Vocalign, but this has never been a problem for me in other projects, and in this project even tracks with absolutely no plugins on them (ie tracks which had already been bounced and were previously playing back fine as bounced tracks) are out of sync.

The offending audio regions have also physically stretched themselves out - e.g. a vocal region that should have been from bar 30 to bar 80 could be showing as from bar 30 to bar 88.

Not at all clear what the "trigger" could have been other than possibly opening the project with a different audio device (e.g. with or without airpods connected?) but normally that's not an issue either. I've not been doing anything with the tempo or sample rate.

Any suggestions?

NB I am aware I can restore a previous version but that will cost me some work so I would prefer to understand why this is happening.