first of all when you have dhcp proxy enabled , there is no need to put ip helper because the dynamic interface itself works as relay agent. So what you really need to do is to configure the primary dhcp server ip on the dynamic interfaces and see how it goes.
Thanks for your reply. The primary dhcp server is set on the dynamic interfaces staff and student as the windows dhcp server. the iphelper address is configured on the 4503 switch for the wired clients. As I said the controller works as normal after a reboot but fail after some time. Do you know if there could be a fix for released for 220.127.116.11
I will post the debug message when the issue arises again. at present the clients are getting ip as I restarted the wlc.