DJM-A9 - Defective Unit? USB Connectivity/Functions?

I ordered a New DJM-A9 Mixer. I received it 3 weeks ago and have been using it in my home office/studio. I have been experiencing all kinds of strange issues with it since I got it. Yesterday I decided to call the dealer which I purchased the unit from. I spoke with the salesman and explained the issues I have been having and he agreed that it seemed to not be working right or malfunctioning in some way. When I bought it I had also bought an extended 5-year warranty but the dealer themselves only offers a 30 day return policy on the unit. Due to the cost of the item (with the warranty it is nearly $3400) I decided to order and pay for a 2nd unit with the same 5-year warranty. At the same time, I created a return for this unit with the retailer. We agreed that I would mail back this unit I have now once I receive the replacement unit and at that time I would be refunded for the purchase of the first unit. 

The issue that I have been having is with the USB Connections mostly. I can only get sound to come from any connected USB source on Channel 1 on the mixer. I have tried everything. 

This is an example...

I have a computer on my desk that is a desktop workstation. I hook it up to USB-A on the Mixer. 
I have another computer on my desk. A notebook PC that I hook up to USB-B. 
I start music or audio playing on both computers (from any application, it doesn't matter which).

Once I do this, I can only hear one of the Computers USB Sources at a time.
The computer which I have hooked up to USB-A I can hear only on Channel 1 when USB-A is selected.
The notebook which I have hooked up to USB-B I can hear only on Channel 1 when USB-B is selected. 

Shouldn't I be able to play audio from USB-A or USB-B on any channels 1-4?
Then also shouldn't I be able to play audio from both USB Sources (A and B) on different selected channels at the same time? I can only hear USB audio on channel 1 and then I have to toggle between A and B to hear either one. This is regardless of what I have channels 2, 3 and 4 on the mixer set to, USB-A or USB-B. 

It is really weird to me just the way that his mixer seems to function. I do not know why but when I hook up my computer to USB-A, all sound from the entire computer (all Applications and the Default Windows Sounds) come out of Channel 1 on the mixer, as long as I have USB-A selected. There is no other way... even if on the mixer if I have channels 2, 3 and 4 on USB-A, all sound comes out of USB-A on Channel 1 on the mixer.

I have (2) Technics 1200's Turntables, a Denon SC6000M and a Denon LC6000. I have each of these devices hooked up to different channels. I input audio from any combination of these devices at any given time. Using the mixer's input selection, I choose what I want to have active at any given time. As I mentioned at the start of this post, I recently bought this DJM-A9. Prior to this I had a Denon X1850 Mixer which is Denon's most high-end mixer and is very comparable to the DJM-A9 in many ways. The X1850, it also has Dual USB but when I would hook it up to my Desktop Workstation, it would create in Windows an audio device for each of the mixer's channels. 

Denon 1/2 (would be channel 1 on the mixer)
Denon 3/4 (would be channel 2 on the mixer)
Denon 5/6 (would be channel 3 on the mixer) 
Denon 7/8 (would be channel 4 on the mixer) 

The way I listen to audio is probably kind of odd. My Main Desktop Workstation I have 3 monitors and a TV hooked up to it so I tend to do several things at once. For example...
I could have a song playing on my SC6000M at low volume on mixer channel 3. 
I could have at the same time a chrome window open with Netflix playing a movie. 
I could also have Discord open and could be on listening to and participating in a conversation.

With my Denon Mixer, I could go into the Windows Audio Mixer (or I also use a free app called EarTrumpet to make it easier) but I could go in and assign all Windows Sounds to use Denon 1/2. So all Windows sounds, incoming email sounds, notifications, things like that would come through channel 1 and I could control the volume for that right there on the mixer. I could set Denon 3/4 to Chrome so Channel 2 on the mixer, I could control the volume of the movie I had playing in Chrome. Denon 5/6 I would have hooked up via Digital connection to my SC6000M and have a song playing on it, Channel 3 I have 'digital' selected for the input and can control the music volume. Denon 7/8 I could set to Discord and all sound from the conversation in Discord would be Channel 4 on the mixer. This worked great for me! A big reason I even have a mixer like this is I want some kind of hardware control where I can adjust audio. I keep the mixer in an upright position within arm's reach at the right side of my desk (I am right-handed). It is kind of right near my computer mouse, and I can control audio on the fly as I am working and listening to music/audio. 

With the DJM-A9, the only way that I can get it to work is that all audio from my computer comes out of Channel 1. That is it, there is no other option or way to route it any other way. As I said above, I can get USB-B to work from a separate computer but only on channel 1 and only by turning off USB-A effectively. 

Is this how it is supposed to work?? 
I told the Dealer Salesman that I was not sure if this is just how it is or if my unit specifically has a malfunction. I can get sound to come out of the unit and I can get it to power on, all of that is okay but the USB Routing seems off or it doesn't work as it seems it should as far as USB goes. It seems that it should work or otherwise USB-A and USB-B would not be shown or would not be an option on Channels 2, 3 and 4. It says that this is a 8/10 device and if all USB audio comes out of channel 1 only, it is not a true 8in/10out device.

I do have the 'Pioneer DJM-A9 Settings Utility' Installed though it does not really seem to do anything that I can notice. I also updated the firmware immediately when I got it because I saw there was an update available... it has 1.02 currently.

Also, another issue that I have is I have it hooked up to my computer, USB-A. I do have it working but with the severe limitation I mentioned where all USB audio only comes out of Channel 1. I will have it working and then when I open certain applications which use the audio output and/or microphone, it drops the connection to the mixer. It still shows the audio (if you open Settings/Sound/Output) you see the A9 and you see the meter moving (within Windows, not on the mixer channel itself) like it is receiving audio but you cannot hear it. I have found that if I go into the properties of the mixer and then it says "Allow apps and Windows to use this device for audio' if I hit 'don't allow' and then wait a few seconds for it to disable the A9 and then hit 'Allow' and wait a few seconds for it to connect again then it will start to work again... some apps or sometimes this does not work and I have to restart the mixer and then it works or sometimes I even have to restart the computer entirely to get it to work. This seems odd to me. I have particularly noticed this happening when I open and close apps such as OBS Studio, Zoom, Virtual DJ etc... It is very frustrating because whenever I open or close some applications, I have to reset the audio hardware/settings which is frustrating. I couldn't even imagine a live DJ type scenario where someone was playing live with a crowd... I am just sitting in my office. 

Is this how these units are supposed to function? I have been having major issues trying to get it to work right. Is anyone else using this in a way that I am and experiencing these types of issues?? I filed a ticket with Pioneer support and am waiting for them to contact me, but they said I would get a faster and possibly better response here from the community.