Now I understand. The problem was caused by enabling Cloud Sync on devices that already contained data. This caused the duplicates and also the problem with the missing lyrics. Version 3.7.2 tries to salvage this situation and if it can‘t it writes lyrics that can not be assigned to a song to the folder Restored Lyrics. You could check if you can find it there.
Of course the better option would be to restore a backup file on one device while all other devices are still connected to the Cloud.
Please take a good look at the manual on how to enable Cloud Sync without issues: https://stagetraxx.com/user-guide/cloud/#working-with-icloud-sync