i musta gotten a bum pair of deer stags. not only did they take at least a week of walking around with blisters on my heel, breaking them in, but they set off the detectors every single time i walked through them. not all at the same airport, either, so it wasn't just super sensitive machines at one spot, or anything like that.
now that they're 3 months old, the cloth inside of the left heel is worn off, and down to pure plastic scraping my heel again, now that the blister is completely healed.