John
Your impatience is showing through, as is your frustration. Let's stop for a moment and analyze the problem. It may also be useful to take this off the forum and communicate direct.
Facts:
You have a K3/0 Mini. Some questions:
1. Do you connect the paddle to the Mini, or to the RRC Control Box?
2. You are using the attached USB cable and the Microbit ports for radio control and Winkey.
3. What version of the K3/0 mini firmware are you using? To see what is in your mini, you have to disconnect the Internet line to the RRC box, turn the Mini on, then enter the Config menu. If you leave the Internet line connected, you will see the Firmware version of the Remote K3 unless RHR has disabled it.
4. If you aren't using Firmware 5.38, you should update. There were several fixes related to ERR KEY in Firmware 5.38.
My view now is that this problem is not directly related to RHR or Remote Rig units, but has to do with your equipment, either the Firmware or the station setup. Something is causing the ERR KEY message. ERR KEY is telling us that the keying line is being grounded by something; if it was an RHR problem they would be having LOTS of complaints. Since you seem to be the only one with the problem, my conclusion is that it must be local to your setup. What is wrong, though, is escaping us.
Dennis W1UE