Ok, that does indeed seem very loud.
There's only really one more thing I can think of, and I can't really check it out because my cuemix is a different version from yours.
I read that clicking the focus button allows you to see various effects and processors for that particular channel.
Is there any chance that there is some kind of boost, compressor, eq, anything like that turned on through cuemix?
I find it hard to believe that it's a fault. It just doesn't seem like it would be, you know?