How can we remove an Assigned BPM worklist item for a purchase order that has already been approved?

Summary:

We have a user with an "Assigned" Approve Purchase Order BPM worklist item but the PO has been fully approved and closed and this "Assigned" item shows as fully approved when we open it. No matter what action we try to take from the BPM worklist as administrators, we are not able to Withdraw, Reassign, or Suspend this item. We also do not see this Assigned item in the Transaction console (We only see the fully approved transaction).

Any idea how we can "clean up" this BPM worklist item?

It does not appear on the bell notification

And we have run the Synchronization process