How often do you have it serviced?
Sounds like a tamper issue so either contact the installer, a reputable company or get the ladder out but beware there's high voltage around the pcb.
Personally I would only drop the power to the detectors.
I'm not sure with these panels but there will most probably be an output that resets on arm/set or something similar (pulse output perhaps?) that you can programme to drop the power momentarily on setting.
Worst case, you cold wire in a small unobtrusive switch to interrupt the 12v and mount it through the casing at the bottom or something.