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Ibrahim, I got the workaround to work. Here's what I did-Goto Policy->policy elements->Results->Client provisioning->resources->Add->Anyconnect configuration->Windows/OSX-Now replicate the current settings that you want in this new policy-Then apply ...
I had the same error and got it to go away when I disabled RADIUS accounting on my anchor controller. I de-selected accounting all together for that SSID. Make sure your client is de-auth'd on both WLC's and try the CWA page again.