I recently ordered a RRS ballhead. The BH-40LR. I love this ballhead. I really like the top loading, lever release and the ball locking lever (instead of a knob). Also, it's size and weight. It is great for the smaller SLR's and is perfect for a hike with a carbon tripod. It came without tripod mounting threads. I have bought a lot of their products for a long time. Including the old days with the "Camera-Nazi". I've never had a problem before. They quickly replaced the unit. Their whole business model is innovative quality. It is inconcievable such a defect could have been shipped. If there was any quality control, it would have been noticed. I forgive them. The real irratation was the attitude of the guy who answered the phone. It was like I didn't know the difference between threads and a hole in the ground. And if the threads were, in fact, missing, well, "stuff happens".
I may be making a mountain-of-a-molehill but I hope this fine company keeps their eye-on-the-prize.

What was the defect?

I would guess this:

No mounting threads, just a hole.

Mistakes happen and forgetting to tap a hole is not a huge deal and not a sign of no quality control. You said they replaced the unit so I don't see any further issue there.

The rep having a bad attitude however is a valid complaint. I think you would get further by talking to his supervisor instead of coming to a forum.

I have had nothing but courteous, informative, prompt service from RRS, by both phone and email.