Looking into it a little further one that failed as you can see from the below on BIG IQ (bottom is oldest) the last request which is a POST request all others are GETs has a different pool member;
The post request I believe is also the request that has the value in the payload and it seems to be the one request that goes to a different server. I also can't see the reference from the blody logged anywhere at all and I've sent well over 200 requests where the same value above is in the payload yet it doesn't log. The persistence table shows the last destination server as the one where the final POST message is sent to so I assume it changes as it reads the requests
Does the last part that scans the payload work like an elseif statement rather than a statement on its own? Would it be worth also looking for the values from the sever response as I believe the value can be in there as well.