Is my persist record getting ignored?

I think there are a couple of things going on here. First, I've figured out that I can simply combine the two event handlers into a single iRule, and assign that iRule to a universal persist profile. I also figured out how to create a rule that shows which member of the pool has been selected (LB_SELECTED and LB::server addr). I can see that my persist records are being honored correctly, which is a relief.

The problem is that I have two servers in the pool, and they use an incrementing sequence beginning with 1 for the transaction ID. The transaction IDs occasionally coincide, which is why I put "persist delete uie $Transaction_ID" in the request check. However, once the persist record is deleted, the LB want to use the other server in the pool and sends the final request of the transaction to the wrong server. I've found that if I don't include the delete statement, the transaction IDs of the two servers overlap and an existing persist record is reused. This sometimes causes the LB to send the requests to the wrong server.

Is there a way to delete the record after the decision to forward based on the persist record has been made? All I have to go on for the final ACK back from the server is a 200 response (i.e. no transaction ID to tie it to), so I have to act based on the request.

Thanks.