Ludwig, my issue was related to large databases when a data field count that is displayed (e.g. artist, composer etc) reaches a very specific number (256). M have found it and will fix.
@ Tonepub, assume both HDD's are fully functioning in the TwinStore? Have you rebooted everything ?
Can you take a screen grab of the debug screen and post here?
Also, access the share as Ian suggests and see if the file structure for albums, artists etc is there.
Can you confirm that albums are definitely missing from your library and that that the core simply hasn't moved them ?
You don't have a weird focus set that is fooling you ?