I have a client with 13 devices, mostly iPads, and have been seeing this very strange problem where they will remain associated with an AP but suddenly stop passing IP. I saw this happen myself while pinging two of them from a wired PC. They stopped replying to pings yet the Balance One controller said they were still associated. Disabling and re-enabling WiFi on the tablets fixed it, for now. Other tablets associated to the same AP pinged fine during the issue with the others. This happened on an AP One AC mini and on a 300M. One tablet had been associated for 3 hours 45 minutes in case that matters.
Any ideas what could be wrong?