In short and simple terms Martin you have a 'stuck' contact on your front door.
Give it a gentle tap, it'll more than likely start to work again, if it does or not it needs replacing. It will happen again.
The information you have given is very concise, thank you, to an alarm engineer correct information is half the battle of fault finding.
The control panel type has no bearing on the fault you describe.
acorn, January 2010