Your camper has an advanced car alarm fitted by the factory. The system includes motion sensors for the interior which will detect any movement inside the van and will trigger the alarm ( neighbours wont be happy at campsite) if movement is detected.
If you wish to lock the doors , please dont use the remote button on your key, instead press the lock/unlock button on the drivers door , next to the door lever.
This way all the doors will be locked but the motion sensor remains switched off and you ( and the others at the campsite) can enjoy the night and have a good sleep.
Also please be aware that flies( and any similar size or bigger animals) can trigger the alarm. If your van goes off randomly time to time when its parked and locked by the remote its worth checking if you dont have an uninvited passenger inside.