i think g2core uses change for the probe, rather than caring about any particular polarity of the change.
odd that it is failing to register. how are you wiring the probe?
if you are wiring to +5v and have hardware debouncing in place might the probe failures be because the cap is taking too long to charge up? or perhaps that your probe has too much resistance?
have you tried wiring to ground and using the internal pull-ups? As mentioned, the g2core doesn’t care which way around it is (at least that’s what I recall from when I looked at the code a couple of weeks ago).