It can also happen when you previously worked at a national lab that works with those kinda things, and the one lab-wide tour day resulted in trace elements getting on your clothes... Or it was forced to happen because paranoia thinking I'd smuggle something when really, my income was being sabotaged & made it clear I was being targeted and wasn't sure who was behind it at the time. Still pretty sure it's a "multiple sources of targeting. Both right wingers & a mouse" scenario