Have you tried enabling the TCP-MSS feature globally at the WLC or at the 1810 AP?
I'm not sure if it will apply to the RLANs if they're on flex local switching but it should. Give it a try and let us know if that helps.
Basically the AP intercepts the SYN packet of the TCP handshake and replaces the TCP-MSS proposed value for the one you specify, therefore preventing fragmentation.
If that doesn't work, then you can try the "ip tcp adjust-mss 1360" command at the gateway if it is a cisco router or switch. It'll perform the same function.
hope that helps.
** Please rate helpful posts **