And that is exactly the issue, and exactly what the German police warned about when they were testing machines years ago when the US forced them on other countries. Tissues in pocket, pleats in clothing, slight sweat - they all cause issues, and result in false positives and thus more hand checks.
As noted above, I cannot use these machines at all. But each time I decline, I still have to wait for a hand screening as the screeners are busy checking those who alerted the machines. (And there are generally fewer female screeners) My travel partner is pulled about 95% of the time for a hand check, with no obvious reason.
Unfortunately this is a case of the prediction coming true, and was the reason why the original machines were not installed.
MUC staff by the way was again good to me this week.
Article on the original machines in part stated that in about half the cases there was a false alarm: 15 percent had a real alarm, 5 percent unclear why they alarned, and only 31 percent of passengers had no alarm ie green light.
In knapp der Hälfte der Fälle soll es zu Fehlalarmen gekommen sein, hieß es 2011 aus Kreisen des Bundesinnenministeriums. Bei weiteren 15 Prozent habe es sich um echten Alarm gehandelt - bei fünf Prozent blieb die Ursache für die Meldung unklar. Nur in 31 Prozent der Gesamtfälle gab das Gerät grünes Licht, weil es nichts Verdächtiges bei dem Passagier gefunden hatte.
https://www.sueddeutsche.de/reise/si...-ein-1.1531359