ATMOS tracks out of sync when not in 2.0 or binaural

I have been working in Dolby Atmos for a while and all was well.
The tracks in the project I was working on started going out of sync. If I set the mixdown to 2.0 or binaural it’s fine, anything above that and the sync issues start again.
If I load up an older version of the project it is fine as are other Atmos projects.
Something changed but I cannot figure out what it is. I have checked Asio Guard etc and that is the same it was in all projects.