I've got the same issue with mine. Total PITA really and common across all the Golf MKIV platforms. Post up the cost of the parts if you do yours as I might get around to mine if its not too much cash.
I think I've got the same on the Passenger side. I presume the microswitch also tells the alarm system the door has been opened so not to re-arm after 30 seconds?
Every time I only open the passenger door to do something the bloody doors lock after 30 seconds of 'inactivity' and the alarm goes off, a royal PITA!