I have a similar problem. I added an AP902 to my 2860ac to extend coverage into the garden, this was after trying various lash ups using old routers from Fritzbox and BT. Worked okay with one AP902 and the 2860, but adding another AP902 caused the 5Ghz band to drop speed to anything from 1mps down to nothing, this happens on Android, iPhnone, Windowa Linux and Mac OSX. I initially thought there was a problem with the new (used) AP902 but swapping them over confirmed both AP902s are the same. Switching 5GHz WLAN off and on again will often bring it back on that device, but it will then vanish on the other one, I seldom have both working.
curiously upload speed from teh device is fine and runs flat out. I've tried pushing profiles from the 2860 using central management, configuring by hand, moving away from the DFS bands, re-siting the AP902s and dropping down to 20/40 MHz bandwidth, nothing has worked.
If anyone has any ideas I'd love to get this to work, I'm now out of ideas though.
P.S. I've always used IP>MAC binding rather than fixed IP addresses, makes things much easier when doing a factory reset for one.

What version of firmware are you using with the AP902 please