I noticed that with the GPIO adaptor you can end up with phantom inputs if a controller is not connected. In order to stop this I have soldered a 10K resistor between the DATA and VCC pins. As the data line is active low it means if there is no connector plugged in the GPIO adaptor reads all the pins as ‘UP’ or not pressed. This stops all the fake keypresses that it can otherwise detect but doesn’t seem to interfere with normal operations once a controller is connected.
If anyone else can confirm this maybe it is a possible upgrade for future GPIO circuits to include?