Just to post in Tunze defence. They seem to be taking a beating here over this problem, and I think it needs to be pointed out what a great job they are doing handling this whole situation.
I think most people do not understand the engineering, materials science, and manufacturing involved in these products. Especially for a relatively small company, you can not always foresee what problems in manufacturing and real world use might pop up. They are not always displayed in your prototype (not usually made from the same molds, on the same machines, and often not with the exact materials)
I have a friend that builds and maintains molds for plastic injection molding machines. He has build molds that cost more than 6 figures for one part. It amazes me sometimes that smaller companies can even afford to use this stuff. So it means a lot to me when I know they have to spend the money to make and test a new mold.
As a side note, I have various pumps and other products (I won't name names, but not tunze stuff) that sits in a bucket of broken misc. equipment. Some of it has been repaired multiple times, or of poor design, or too loud for real use. Whatever the reason I wasted my money on it and the manufacturer couldn't or didn't fix it. Yet this minor problem (heck, I could fix it with some glue) is being addressed. This only solidifies my confidence in Tunze. Even the best product company is going to have a problem once in a while, that's why customer service is just as important as having great products.