Yes it is a very common problem and not just with mk2's but with all vw's your just lucky it acctually still goes down!
Its due to either a lazy motor or the mechanism,best thing to do is take the whole mechanism out (the motor is attached to it) and inspect the mechanism you will see if the wires have frayed,it usually goes where the the wire goes into the motor,theres like a white sleeve if this is mangled then its the mechanism thats knackered,if not then it will be the motor has gone lazy,you can buy the mechanism seperately or you can by it with a new motor attached from euro car parts or gsf,its upto you whether you want to take your old motor off and attach it to the new mech or whether you just wanna buy the whole thing,the mech on its own is about 50 quid from gsf not sure about with a motor but would think in the region of 80 odd quid,hope this helps.
