Although customer set "no" to "DisallowUtf8NonCanonical", WebAgent reject URL encoded query contained "%c0".
WebAgent R12.51 CR01
This is product issue.
If request contains overlong UTF-8 encoded data, such as "%c0", "%e0%80", "%f0%80%80", this requests was rejected because WebAgent judge as BadUrlChars.
This issue was fixed in R12.51 CR06.
Upgrade WebAgent to R12.51 CR06.
URL Access Request Blocks (114493)
The URL access request blocks when you access a URL which contains %c0%af with DisAllowUTF8NonCanonical flag set to no in ACO.