Golok: Sure, it can happen. The solution is very simple. Bad knives don't leave my shop. Never, ever. They do end up in my kitchen drawer, but, not in a customer's hand.
One important lesson I've learned is to hold a knife for a day or two before shipping. It's funny how, everything looks perfect when you first finish up a knife. Going back the next day, with a "new" eye, I'll often find something that I want to touch up before I send it out. And, that's after 20+ years of making knives.
Having a thorough mental checklist of "inspection items" really helps. Customers should learn to look at a knife in a specific way, checking out each item in a specific order, so that, over time, the inspection becomes consistent and routine, and, nothing is overlooked.
A typical checklist for a fixed blade might be:
1) Blade grind height/uniformity
2) Blade grind symmetry
3) Plunge symmetry-This applies to the top grind, too, if the knife has one.
4) Grind- on centerline and straight
5) Point centered on blade and blade straight
6) Blade uniformly finished
7) Solder joint-Perfect?
8) Handle to guard and handle to tang- Smooth and gap free?
9) Handle contouring-Symmetric and scratch free?
10) Bolts and thong hole tube-Smooth and scratch free?
11) Logo application-crisp and clean?
12) Edge-Scary sharp along the entire length?
You get the idea here-you can add more items as appropriate...
Looking at a knife point first will reveal lots of potential flaws that are frequently overlooked.
Hope this helps,
RJ Martin