2 usual problems are that only one is replaced- always replace both, and the other one is cheep bulbs, vw supply 'osram' bulbs which are good but most dealers buy in a cheeper alternative and pocket about 80 pence pure profit over the price of the ones they should be supplying, doesnt sound much but if you sell 20 bulbs a day and make a profit from the osrams, imagine how great ?16 extra is a day for selling cheaper ones!!
Dont skrimp make sure its good bulbs, it makes a difference, especialy to your rear bumper in poor weather and your lights aint working
Taillamp bulb 5W (tinted taillamps 10W)
Brakelamp 21W