Travis,
Not 6x42 FX-3's, but have seen three 6x36's FX-II's fail, one right out of the box, the other two within 100-200 rounds.
Have had several fixed-power SWFA's, and so far the only problem has been one with 1/4 MOA adjustments that actually adjusted around .2 inch at 100 yards.
Last edited by Mule Deer; 03/12/18. Reason: additional info