Error: -536813545:A duplicate backup sets............

Hi All

I have a CAS 2012 fully updated with a dedup store.

And a MMS 2012 fully updates with another dedup store.

I can, from CAS, make backup to both dedup stores.

I CANNOT make backup to CAS dedup store and then duplicate to MMS dedup store.

When configuring the job I get:

Calling Method 'UpdateDefaultbackup Definition'
BEMSDK Method 'CBemPolicy.Update'
BEMSDK Failure Code: -536813545:X8
Error: -536813545:A duplicate backup sets template must use a destination device that can be accessed by the same Backup Exec server as the device specified for the original backup set.

As I can make backups to both dedup stores, I don't understand the error.

Why isn't this possible?