Had a new one this week. Went through security in Sydney Domestic airport. No problems, I've done this many times. All my stuff in a tray, send it through the scanner, and hands in pockets, I stroll through the metal detector. No beep. No alarm. No problem, normally.
Security: Sir, your hands were in your pockets. You can't do that. Please go back through.
Me: It's...a metal detector? How do my hands in my pockets affect it?
Security: Go back through please sir.
I went back through, hands out of pockets, again no beep, and security was satisfied, although didn't explain the hands in pockets and why this was an issue? Any ideas?