We have an idea for this, but in testing it I couldn't replicate it.

Could you try using the options in the Debug menu in Settings for clearing the cache and seeing if this fixes it? You may need to Reset MIXO too.

Should neither work try deleting the MIXO folder in your AppData folder (there's a button in Debug for this).

If one of those does the job, I'll close the idea with an update. Thanks!

https://support.mixo.dj/t/remove-deleted-playlists-from-export-popup