Had the same issue last year. Tried several times to hitch up and jaws would not close. After closer examination one side of the truck was higher than the other do to slope of ground. Adjusted my approach and was successful. These hitches can be timid at times. I don't know if i would agree with Demco that the answer is regrind the hitch.
Kevin & Denise Griffin
2015 Ford F350 Super Duty 6.7 Diesel CC SB, Demco 18K Hijacker Auto Slide, Pace Edwards Electric Tonneau, TST TPMS 507 Standard Sensors, Titan 50 Gallon Midship Fuel Tank
2016 Prime Time Crusader 315RST 5th Wheel, Dometic Slide Toppers