On my NA coupe the nipple on the reservoir had a small crack that was difficult to see, but it leaked. At the time I bought a new one from some retailer that is out of business now (maybe Bavauto). I installed it and guess what, it was also cracked at the base of the nipple. But this version had an internal brass tube reinforcing it. So I cleaned it up, roughed the surface and JB welded all around the nipple to seal the crack. It’s been a few years and it is still holding. Definitely a design defect.