Hello,
As per your query i can suggest you the following solution-
The WCS (and NCS/Prime for that matter) must either be on the same subnet as the WLC management interface or on a subnet that is not on the WLC. Otherwise, the WLC drops the traffic because it received a packet on one VLAN/interface (management) to which it would send a reply on another (such as a dynamic interface which the WCS is on the same subnet.)
Hope this will help you.