My best advice is to call TAC. There are several things that need to be checked and perhaps settings changed, and they have a list of things to go through and do a good job of going through each of them.
My first guess would be to see if you have "Prefer AMON" checked off. We have found that this mode of operation shows close to two times as many clients as there actually are, which may only be happening on newer ArubaOS. Eventually you want this on, but even in the latest image we have found it is still not working well.