To help us, could you follow this guide to turn on logs if they are not currently on:

https://support.mixo.dj/guide/how-to-turn-on-logs

Then go to: Music > MIXO > Logs - and send us the files there.

If there aren't any logs, please Reset MIXO in Settings > Debug > Reset MIXO and import the library again. This will then generate the logs which will show us why the last track is stuck.

Thanks!