2001 Volvo S80 Door Open

I have owned the car for 2 years and this problem is becoming worse! The rear near side door (RHD) keeps sending a message to the computer that it has opened or it is open especially on bumpy roads and all the lights inside the car come on including warning light in the dash. Recently the wife and I are having to slam the door really hard in order for the remoter control locking to engage and the alarm will usually go off when we walk away from the car. It does not matter whether there has been anybody in the back or whether the door has been opened or not this problem keeps occurring and the funny thing is the door is not open and child lock is engaged but the computer still thinks it is.

Any Ideas?