My brother and nephew had the same experience. They were members of a crew in a sailing championship, had all the documents to prove it but were still pulled over by USA immigration and kept for several hours, no explanation. Also missed their connecting flight.
A couple of years ago at Charles de Gaulle airport, I watched as they made an elderly Frenchman in a wheelchair stand up aided by security guys because the bleep went off (metal in the wheelchair??), and remove his shoes and belt resulting in his trousers falling down around his ankles much to his and everyone else’s embarrassment.
Incidentally they meanwhile let a Muslim lady walk through in the ‘full gear’ without so much as a quick pat-down. I don’t understand what goes on at airports anymore.