When I had my Mk3 the false alarms drove me mad and, as others have said, they were triggered by Motorway driving. I did repeated recalibrations and, eventually, they went away.
I still feel the system is unfit for purpose. False alarms result in a lack of trust in the system so, when a genuine one comes along, you are tempted to ignore it.
The Mk4 does seem better in this regard.