U3219Q, KVM USB downstream not switching

I have the above-mentioned monitor that I'm connecting a laptop and a desktop to. The desktop is using DP for video and USB-B for upstream data. The laptop is using HDMI for video and USB-C for upstream data. The USB-C cable is connected to a standard USB port on the laptop so no video is on the USB-C connection.  

I've ensured the settings and pairings were correct in the OSD.  I've also downloaded the Display Manager to both the laptop and desktop and all of the settings are the same in both application locations and match the pairings in the OSD.

I have two keyboards and two mice that are currently connected independently. When I move the desktop mouse from the desktop ports to the downstream ports on the monitor, the mouse works when the laptop is active but not when the desktop is active. Likewise, when I move the keyboard from the desktop ports to the downstream ports on the monitor, the keyboard works when the laptop is active but not when the desktop is active. So that indicates to me that the USB-C connection for upstream data is active regardless of which video input is selected.  

Has anyone else run into this issue - what am I missing?

Thanks