Manual Master Fader Pair mode on GIO not working.

I'm trying to use the Master Fader pair on my GIO running v3.1 to run timed cues manually - that is, running the faders down, hitting 'GO' and then running the faders back up in the desired manual time - but it isn't working. Hitting go, even with the faders down, just runs the cue in its assigned time. Setting the master faders to "Intensity" or "Manual" mode doesn't work either. All other faders on the console work fine. Is there something else about the fader config on the master pair that I need to be looking for?