TVshow – category Year – some entrys are empty

Kodi17 Beta 7 & Theme estuary V2

when I go to TVShow -> right up Category -> Year I have some Year tags like 1969 and when I select them it is empty. I already run clean Video Library and scanned again but this still remains. Where comes the Information that a TVShow within year 1969 should be available and how to clean this up?

Any hint

regards
Brujo