I don’t know Mix, but assuming it pretty much works as all DJ software, there is one thing in your setup that sticks out at me.
You set your Sound API (which I am guessing is the interface driver you want to use for your sound card) to Asio. Yet you speak of the latest Numark DJ IO drivers. So could it be you are picking the wrong driver. I normally use Asio4all drivers for most of my sound cards or the driver that comes specific with the device.
My guess would be that the problem lies somewhere in the driver area. But hard to say for sure without a lot more knowledge of your system.
.
