I had the same exact thing happen again two days ago with another brand new pair of slides. If the guides are shipped nested in each other, front to back, and the adjustment tab is turned to a not-so-sweet spot, then it's almost inevitable that the adjuster will get sheared off. It looks to me like it is 100% a shipping problem. I'm pretty relieved to hear that Blum is aware of the problem and on the case.
Incidentally, I ordered these guides to repair a Rev-A-Shelf trash pullout that came with a Servo-drive unit. It belongs to my in-law's neighbor, so we were visiting this weekend and I offered to fix it. I have never installed one of these units and it turns out that it had botton-mount guides, so I could not do the swap. The installed guides still worked great, but the soft-close pistons had failed. I was able to slide the pistons out of the new (broken) guides and make the swap without removing the installed guides. I've never seen the soft-close mechanism fail before, but as I said, I've never installed a Servo-Drive system before. I kind of expect it to fail again. If it does, I will take the time to document it and get Blum to take care of warranty replacements.