the real danger occurs if the machine stops in the middle of a scan

I'm not a knee-jerk alarmist on science like the left but some common sense skepticism is in order. Huffpo with scientists' questions on the TSA full body scanners. I've been concerned from the get-go about first hand and second hand scanner radiation. The last time I traveled I opted for the intrusive patdown. So here's the crux:

For Rez, the real danger occurs if the machine stops in the middle of a scan, allowing the beam to focus on a tiny area for several seconds. Given that the backscatter works with a wheel rotating at a high speed, and that the agency plans to use the scanners continuously 365 days a year, mechanical failures are likely, he said.

The TSA says that the scanners have safety systems, such as automatic shutoffs and emergency stop buttons, that will kill the beam in the event of any problem that could result in abnormal radiation. How those fail-safe systems work isn't entirely clear.

And with unionized I don't do windows job action TSA workers maintaining them who wouldn't be worried?