New 5th wheel doesn't tow well

Some tow vehicles don't match well with certain trailers. Something needs to change in your measurements or geometries to really fix the problem. Otherwise, you can just try to mask the symptom, which may be good enough to make you more comfortable. I don't know anything about the Anderson hitch you are using, but can you try changing the height of your hitch?

Be honest, you were thinking about a longer tow vehicle any way, weren't you? LOL.