The alarm on my van went off and when I got out there noting was seen to be tampered or open, I reset it and went back to bed. This afternoon I checked and found that if I pulled hard at the front nearside bonnet flap ( a Hymer A class) where it is against the headlight The microswitch set the alarm off. Why should anyone do that? They can't get anything in there or is the alarm just a bit sensitive. I am just a bit paranoid as it is the only new thing I have ever had and the dearest. The only other thing is my neighbour has a long drive over the fence and his Mercedes car has a very deep exhaust note not noisy but very low frequency, can that set the ultrasound sensors in the hab area off?