I got a similar problem with a blank page after a redirect in sitestudio/UCM.
You should activate the trace "httpprotocol" in the System Audit Information page and see if you can find a stacktrace.
In case of an error, you have two ways of defining an error page (and thus avoiding users to be redirected on the backend pages):
-By configuring an error page in sitestudio.
This error will be called only when a page or a resource is not found.
-By overriding the default error page template of the content server.
The template is "ERROR_PAGE"
Hope it helped.