Originally Posted by
gobluetwo
You're in NYC, so LGA, for one.
IIRC, LGA is one of the few larger/major airports that does not have a scanner in the PreCheck lanes. JFK does, as do most others.
As you noted, though - in airports where there is no scanner in the PreCheck lane, PreCheck gets periodically shut down and everyone gets sent through the "regular" line, which includes going through the scanner unless you opt out.