Wikimedia Bugzilla is closed!

In stompPFPPendingProcessorSA.php: 

If the pending queue is shorter than $batch_size, and handle_pending_transaction() pushes one or more pending transactions back into the pending queue, those pending transactions just get back in the queue to be processed again in the same batch. Therefore, if one or more transactions come back from paypal with code 126 or 26, the processor can't quit before it's re-pulled and re-queued the pending items enough times to meet the initial $batch_size. 

The end result does not appear to be damaged by the current behavior; It's just an efficiency problem. Ideally, if the queue is shorter than the batch size when the processor gets kicked off, it would consume each transaction in the queue once, and exit.