Networker is not setting a tape as Full/Read Only during a new backup

I am running Networker 8.2 on a Windows 2008 R2 server attached to a Quantum Scalar 1500 tape library. One of our full backups with a retention period of one year has started to mark the tapes it uses as Full/Recyclable, rather than Full/Read Only - and started overwriting itself when running out of available tapes. So I have been manually marking them as "Read Only" to prevent that from happening. But it seems that the next day, what I manually marked as read only is now recyclable again. Everything appears to be setup properly in Networker.

Anyone have any experience with this?