This kind of thing drives me crazy. I fortunately haven't had this issue with the Zen, but I'll certainly keep an eye open for them. I think the Zen is a fantastic kit, and my customers love them.
How I wish one day one of our suppliers would truly institute some sort of real quality control instead of talk a bunch of jive about how their kits are so much better quality than all the others. Several companies do this, but really have difficulty actually following through with it. I can totally understand the occasional slip up, but there are some kits that just continuously have issues (every company has trouble kits--- I'm not singling out one over the other).
We can't expect perfection from any company, but good grief, if I am going to charge $50-60 for a ballpoint pen, the customer should at LEAST expect that it will fall apart LESS frequently than a 50-cent Bic ballpoint.
Is that too much to ask?