Let's just put out there what most people know but some choose not to consider. These Lippert 5er frames are simply junk. The manufacturers use cheap materials, arguably on the marginal side of structural rigidity, with poor welding and little quality control efforts. Therefore, I believe you could potentially take 10 identical trailer/truck combos with the same chucking issue and need 10 different solutions to solve it. An exaggeration perhaps, but the point is made.
Having read threads on here about chucking, its very clear that no silver bullet exists. Maybe one guy's solution is a new pinbox, but the next guy might find more success with shocks or a better hitch. So at any time, anyone's best guess as to how eliminate chucking is based upon their own success or failure in this department. Chucking doesn't go away...it just transfers where the force is absorbed or felt.
Along the same lines, I find it to be so hilarious that Lippert offers the "Correct Track" system, and they shamelessly suggest that this will cure the axle alignment issues that exist on your Lippert frame. I might ask why one should have this issue in the first place, and instead of Lippert offering a costly solution, perhaps they should just do better in the first place.