Strange Alarm fault

So this week my TF passed its MOT . I came back from the test station and parked in the drive with the top still down . Feeling 'Chuffed ' that the car had passed I had some lunch and later on decided that with leaden skies approaching I would put the TF back in the garage, which I might add is about half a mile away. Reversed into the garage , locked it with the fob and as I closed the garage door the alarm started going , ahem I thought . Stopped the alarm with fob and checked that I hadn't left a window open . Locked car again and pulled the door of the garage and , yes you guessed it , the alarm went again . Same procedure as before only this time I stayed in the garage and pulled the door from the inside and ……..yep the alarm went again ! Every time the door of the garage was shut the alarm sounded . As I say the garage its parked in is a jog away from my house so , not wanting to annoy the surrounding neighborhood I locked the car with the key and pulled the door without any further problem . Its not as though the door of the garage was slammed shut as I tried several times to close it without success . The only thing I've done of late is change the o/s drivers door latch due to what some folk have described as the 'machine gun of death' noise from the original latch on locking the car . The alarm has been reliable on my TF up to this bizarre episode so, guy's what do we think ? I'm off to France in it later this year and I don't want to annoy the locals any more than Brexit already has ! ! !
:nonod:

John

Strange.

Roof up or down?

Roof up . The garage is in shade and it was just before the door was fully closed before the alarm sounded . It's just the totally bonkers system on these cars . :nonod:

Have a read of https://www.the-t-bar.com/forum/21-david-aiketgate-s-guides/11201-alarm-system-how-to-test

It may help you narrow it down a bit. Sounds most like a volumetric false trigger - possibly the garage door closing is giving a Doppler shifted RF reflection that the volumetric sensor interprets as a movement within the car.

Have you tried parking the car facing the opposite direction in the garage and closing the door?

Yes I have read that and yes I will drive it into the garage and see if it still does it . You may be right about it . Cheers

Chaps,..... if this is the cause does it mean if the car alarm has gone off in windy conditions and the internal vents are open this would trigger the volumetric sensor?

@ Keymaster , Well judging by the lack of air that comes through the vents when traveling at speed I don't think that's the issue . I have tried my TF since and the alarm hasn't gone off so I think it was what g7nbp said . Thanks for your thoughts guys .
John.