Cat 5 Compatibility Issues

I have a unique problem, and I am hoping the experts on the forum can possibly provide the answer.

I had a Hammond XK1c, which is a midi out only keyboard and had no USB…only DIN. I used an Atemp midi controller

and then USB to the PC. When I had that setup, the Atemp would not work in any port except the 4 ports on the face of my desktop pc. In any other port, (I have 10 total) the resources would be all over the place. Plugging to the front allowed me to use B-3X, but only in those 4 ports.

Fast forward to my current situation. I replaced my Hammond XK1c with a Hammond SK Pro. The Pro has a USB port as well as DIN in/out. I started to accumulate too many extraneous devices on my keys and wanted to simplify my rig, so I purchased a U23X50, which is a 4 port USB extender over Cat 5 cable. I have 3 ports in use…my Integra 7 sound module, my Keylab 61 MKII, and initially the USB from the Hammond SK Pro. There was a ton of interference and the resources were again all over the place. I removed the SK Pro and immediately the resources settled in at around 46%. I ran a USB extension to the front of the PC from the SK Pro and the resources jumped a bit to around 54%, but B-3X and all other VSTi’s functioned as usual. I removed the other devices and ran just the SK Pro and…same issue. Unplugged the SK Pro, plugged the others back in and I was immediately back in business. It’s great to have the PC and mixer situated back behind me, but having to separately run a USB from the SK Pro is annoyingly frustrating, and exceeds the recommended 15’ USB cable length. I am trying to understand why and maybe fix the issue.

Both times this issue has reared it’s ugly head was with my Hammond XK1c with my Atemp and now with my Hammond SK Pro. I know there are a few running this type of rig where things are offstage or situated away from the rig with connection by Cat cable. I have been through the manual and floated the question to @dave_dore,but since this is new territory, I was hoping that someone can help me track down why this connection seem incompatible. I will do my best to answer any questions.