Cisco :: 4404 LWAPPs Dropping Clients With Only Moderate Load

In my district, I have 11 schools running many LWAPPs and WAPs, connected to a single WLC and managed by WCS.Only the 4 LWAPPs in the administration building experience the following issue:When about 8-10 WiFi devices are present on one AP in the bulding (which usually happens during a meeting), all APs show a "Load Threshold Violation Error" and start dropping some clients intermittently and refusing to connect some new clients. There doesn't seem to be a pattern as to what sort of clients drop, or which ones can connect or re-connect. My WLC is on the same subnet as these LWAPPs since it is in the same building.
 
If I reboot the APs, this sets things back to normal for a while, but eventually the APs will show the same errors and the same connection problems occur. I have tried adding an LWAPP to our Boardroom, which is generally where users are located when the WiFi drops. For a while, this solved the problem, but it has since returned even with the additional LWAPP. Currently, I have all four LWAPPs in this building set to AP Mode H-REAP, as I do in my other schools. I understand this is normally bad practice; when your APs are on the same subnet as your WLC, generally those APs should be set to AP Mode Local. However, in my case, Local causes more drops and connection failures than H-REAP, so H-REAP is the closest thing I have to a "solution" to the problem.
 
I have checked the logs on my WLC and in WCS, and do not see any error messages besides the load threshold violations. I have tried increasing client count, and adjusting interference settings, but nothing seems to work. All LWAPPs are AIR-LAP1131G-A-K9 on IOS12.4(18a)JA2. WLC is Model 4404 on 5.2.193.0 firmware.