There are many OIDs and MIBs on the Internet to get same information from devices.. i guess because there are many different version of the devices.
In my case, i solved with below OIDs.
there are two MIBs, CISCO-LWAPP-SYS-MIB & AIRESPACE-SWITCHING-MIB.
The OIDs i wrote are from AIRESPACE-SWITCHING-MIB and the OIDs on the Internet are usually from CISCO-LWAPP-SYS-MIB.
I searched what AIRESPACE is, and it was a vendor that CISCO merged in 2005.
I guess at least, by Ver.22.214.171.124 in WLC OS would associate with AIRESPACE-SWITCHING-MIB. and this MIB might not support the number of associated AP and client.
I strongly recommend you to upgrade OS.