Journal or Journal Receiver not available

We have a journal that is system-managed, but the receivers are manually deleted.
We then changed the journal to be Delete Receivers *YES and since then receive the message CPI70E6 (Journal or Receiver not available, Reason Code 01).
The 01 indicates "A lock conflict on either journal &1 in library &2 in Auxiliary
Storage Pool (ASP) group &13, or receiver &3 in library &4, prevented the
system from either determining if receivers were to be deleted by the
system, or from deleting the receiver at this time."

This seems to be happening when the receiver has filled up, a new one is created by the system, and the old one detached.
We have changed the Delete Receiver Delay Time from 10 minutes to 30 but it hasn't helped.
The weird thing is that eventually the detached (status=online) receiver does get deleted by the system.

When the message arrives (which would be after 30 minutes of waiting, based on the Delete Receiver Delay Time setting) we do a WRKOBJLCK on the receiver and there are no object locks at all.

Has anyone seen this? What could take the system 30 minutes to delete the receiver?

Any suggestions?

TIA,

Tom Garvey