ClientMatch will not necessarily help to resolve this issue. When the user moves from one AP to another, the user is forced to reauthenticate. The purpose of ClientMatch is to help solve the sticky client problem. Traditionally, user devices decided when to hand off to another AP based on factors such as signal strength. With ClientMatch, it allows the APs to decide when to hand off a device to another AP removing the sticky client effect.
I know this doesn't solve your problem, but it will at least save you the trouble of upgrading to early release code and still having the same problem.
I'm curious, how big is the room that 2 APs are located in? Is the room device dense? Typically positioning 2 APs in the same room causes interference and channel conflicts, although ARM will make adjustments, it still isn't considered best practice.
Thanks and good luck!