I was in pre-check line on Sat. 6/11 at 5:00 AM (JFK T8). All lines were very short. At the end of the P-C conveyor belt a family (5 or 6 people) with LOTS of bags were organizing their shoes, belts (which, of course, they removed) as well as their bags contents; this blocked conveyor belt movement. [P-C is a great system if administered properly.]
I returned on Tues. 6/14 at 9 pm. P-C was closed, lots of LAN pax on long check-in lines. I did notice 2 CBP agents (shirts* marked CBP) were watching pax as they cleared TSA; what were they looking for? [I've rarely seen CBP when I clear security, usually between 2 pm and 5 pm.]
*These agents had dark clothing, don't CBP wear white shirts?