S&W recently won the BATFE contract, beating out Glock and Sig. Sig filed a protest when they got kicked out for a lack of reliability and some of the paperwork may shed light on the NYPD situation.
The BATFE testing involved both full size and compact models (the agents get one of each). A portion of Sigs protest (after they whined about an excessive emphasis upon reliability) dealt with perceived remedial actions allowed to S&W. BATFE countered, noting that a compact weapon experienced a number of malfunctions, but that the tester self diagnosed the cause as shooter induced and requested that the backstrap be changed on her weapon. When that was done by the test proctor, malfunctions ceased. Since that was an adjustment to suit the weapon to the shooter (required part of the weapons specification) rather than actual mechanical adjustment to the weapon, that was within the testing protocol.
Perhaps that's the issue with NYPD, as noted by some earlier, thumbs in the wrong place, which backstrap changes can correct (sometimes-others the grip has to change).