Do you have any unecessary wifi repeaters/etc nearby? I have had these problems in the past and switching off such things really helped. See: Un-official LEVEL MODE MARCH MADNESS Challenge - #95 by leebo
There were comments/threads previous to this from where I got the idea. I use an ant+ dongle with a 6’ cable also (though after switching my repeater off I no longer use the cable and have the usb dongle plugged directly in to my laptop that is about 12 inches in front of my bars). Win10 machine but probably a similar vintage to yours, and a Kickr Core bought in Feb 2020.
Just a thought…
L