This could be a cable issue. Some of our cables are designed for 3-wire connections and loop back other signals so that whenever the cable is plugged in, it looks like there is a device connected to the other end of the cable.
This is not an issue any more than it is with printers or networks. There are no three wire cabling used with GEMS installations to my knowledge. If there are, then those installations are not correct. I woudn't expect a printer or network to work with incorrect cabling either.