Vivaro central locking is haunted? goes on and off of own accord?

I have a 2002 vivaro diesel only 44000 miles,well serviced but in the last few months the central locking has become haunted in as much it can switch itself on and off at any time, when ignition is live or the keys left in when off, some times the switch on the dash works and sometimes not. I have a neighbour with a much newer same van who says he experiences the same poblem. can any one please remidy??. thanks alan....