Error when sharing deduplication storage from CAS server "Sequence contains more than one element"

all instances Backup Exec 2012 SP3, all up-to-date via liveupdate.

Have a CAS server sharing its deduplication storage folder to 2 MBE's already.

Want to share to an extra MBE, upon click OK to share, resulting in the message "Sequence contains more than one element", from there can only cancel.

Restarted all (incl. deduplication) services already, does not help.

Could not find any reference for this message in forum or on www.

any explanation & solution welcome.

Ben