My 2014 3500 did this also. I was on holidays sitting in camp and looked over at the hitch and bumper. Bumper corners were touching the box like the OP and the equalizer hitch was angled down a bit. The truck was new then. I had to jack up under the the equalizer hitch, and tighten the bolts. Shockingly they were VERY easy to turn with just a regular combination wrench, definitely not properly torqued at the factory!!!
I’ve run the Curt commercial HD hitch on that truck and the 2018 3500 after that. I liked them and attempted to put one on my 2023, but Ram changed the frame just a little and it wouldn’t fit nor did they have one that would fit. So I’m running with the OEM hitch on the 2023 for my 15K RV. The 2023’s rated at 23,000lbs/2,300lbs tounge though, an increase.