Tracks Removed and do not come back

I have my music on a NAS and access via mount point. At tumes if the NAS is offline and you try to play a song it can no longer find, it gets removed from the database. Typically a rescan would bring it back into the database when services are restored but lately on my linux LMS it's not. My old method of renaming the folder, rescanning, renaming the folder back and rescanning hasn't worked.

A full rescan takes over 6 hours lately.

Im running LMS on debian odroid