In the past three years, I've purchased about 10 parts from list
vendors (bus depot & go westy).  Of these, I've had problems with 4:

1. A tailpipe that didn't fit.   It sat in my closet and rusted out
in about 6 weeks before I got around to returning it.

2. A radio antenna.   It disintegrated within a year.   I have since
put on a 20 year-old used OEM antenna I got from a u-pick yard, which
is still in great condition.

3. The heater control valve.  This one failed in the open position
last week in 100+ degree ambient temperatures.  It was about 2 years
old.

4. A new distributor that was the wrong model.

So, what's the deal?  Am I having unusually bad luck?  Would I get
better quality parts from the VW dealer?   I hate paying 2x to 3x the
price, but to be honest, if the OEM parts are better it's worth the
money...