Perhaps it is being jammed?
Are you saying the onboard keypad also does not work correctly , I don't know this alarm , I think it's DIY alarm, but just giving you ideas
Maybe where you live
Here Sounders are good especially with perimeter protection , internal sounder is a must
So many DIY installs have no sounder internal , total waste of time
And no coms
You have to have a sounder , doesn't have to be 120db and the keypad won't give you an intruder tone
Personally I would want the internal sounder and bell delay external sounder
Only problem you might get is the resolution may keep trying to switch u til it finds a compatible one but you have switch to make it stick to source output