The OUTPUT-GPIO-1-ON/off piBeacon Model parameter when setting a new device only appears to turn on and off a given GPIO pin if "OUTPUT type" is set to invert.
This, I believe, may have been a problem for some time as I have only just got around to diagnosing the problem since weeks back when it first appeared.
I have tried setting "OUTPUT type" back to normal again and the problem breaks again. I have also tried creating a new OUTPUT-GPIO-1 device on a different GPIO and the issue is the same - only able to switch on and off when the "OUTPUT type" is set to invert, otherwise it is always 0, and then only able to be set to 1 using the gpio command on the rPi itself.