FortiAPs with suddenly high lattency and packet lost

Hello Everyone, I have a problem with 12 fortiAP221B with 5.0.10 and the controller is FG200B with 5.0.12, I use WPA/WPA2-Enterprise with RADIUS, I have 4 SSID, 3 in bridge mode with radius and one in tunel mode with preshared …… The wifi never have worked fine .. The main problem now is that all working more or less fine when all starts go slowly because appear high latency ( between 400-100 ms) and packet lost in all the devices that are connected to this FortiAP and later( 15-20 minutes) starts to work fine again … I tried many things to deactivate all rogue ap, radio resource provision and Client Load Balancing( Part of this never have worked)… With profiles and without them …. TX power manual and automatic…. Increase the authentication time …… Put the AP manualy  one channel trying to not interference with the nearest ones …. I think that there are many people with similar problems. I have waiting many time for a firmware to resolve all the problems but the last one doesn't do that and The only thing that I can do now is to upgrade the Fortigate200B to 5.2.3…, but I have no hopes of solving the problem. Thanks in advanced.