Seems like it's a matter of the metal on the deck that the adjusters bolt onto bending outward over time. If it were mine, I'd try removing the wheel, put a block of wood under the deck on one side, and apply pressure by maybe stepping on the axel to bend it back downward. Do a bit at a time, slip the wheel back on and see if it makes any difference.
You can use the wheels for the HRM/HRB215s that have bearings on these mowers. You have to get the longer axel bolts that are used on the rear wheels of these mowers to put them on.
If you look at the after picture in my post on changing tires, that's what I used on that HRT216.
Not to hijack your thread, but just for grins, you can use those same axel bolts to put duals on an HR214 or HR215.
Should work nicely on soft sandy ground.