Veritas alarm beeps and goes off after being set?

Hello,

My Veritas alarm has worked find since it was installed a year ago. However, last night after being set for the downstairs it started beeping in the middle of the night for about 30 seconds and then activated. It did this twice (saying zone 2).

I checked for anything that could have moved or got in the way of the sensors but there was nothing. Does anyone have any ideas before I call out the engineer?

Thanks

Paul