As mentioned, you need more tongue weight on the TT. THis may be because the utility trailer has TOO much tongue weight, lifting the nose of the TT.
Also, not all TTs are suitable for double towing. Are your axles near the center? If yes, this is not good. You need a TT with a long wheelbase, where the wheels are about 2/3 of the way back.
Also, check your actual weights. Your TT won't weight 5k. Dry weights really are just for marketing, and don't include a lot of regular features. Once you get your tongue weight up, you will probably be over GVWR of the Yuon, and as-is, I am suspicious you may be over GCWR now.
You are right about the hitch: I high-dollar hitch is an expensive band-aid for a poor combination and/or setup. Fix the root problem first, then maybe add a hitch to make things go better under adverse conditions.