Bad vibes?
Thi DEFINITELY has all the hallmarks of a Keyless entry related glitch. For insurance purposes, I had to upgrade my standard Dodge vehicle security (keyless entry) for a Thatcham Class One system when I imported my truck into Europe and I make regular trips across the English channel between France and England with my truck on a RoRo ferry. Any vehicles with the alarm set will usually trigger due to ship-borne vibrations when underway, so by manually locking the driver's door you get some vehicle security when unattended, but you MUST remember to unlock the vehicle the same way, otherwise the Keyless entry (or after market (or even both systems) default to thinking "something ain't quite right here, so when in doubt sound the alarm, disable ignition circuits, enable vehicle immobilise mode etc... " Believe me you only do this once as it is embarassing... . Twin Grovers echoing around the car ferry for 30 seconds continuously at full blast is no joke.
Once done, never ever forgotten... .