Honda mower HRR2169VYA front wheel issue

Hi~
We've tried time and time again to tighten all of the pieces to the wheel assembly on our mower (serial number MZCG8689961). I found a posting for similar issue for the HRR2167VKA mower and tried to use the diagram that was posted to identify the problem area. The wheel itself is not loose. It is all of the pieces held together by the T-40 TORX TYPE SPECIAL BOLT (at least according to the HRR2167VKA diagram I am looking at.) All of the pieces are present, and none look terribly worn. We bought the mower in June of 2013, so it's not that old. We've take the wheel off, tightened the T-40 torx bolt (though admittedly, I don't have the tool that I probably should have - I just use a screw driver to hold it still while I tighten the locking nut on the inside of mower deck), but it's nice and tight. I get about halfway through the lawn before the wheel is wobbling all over the place. The adjuster arm ends up facing downwards and the wheel is rendered useless. Any suggestions? Are the parts listed for the HRR2167VKA the same as those for the HRR2169VYA? Please help - this is driving me CRAZY!
Thanks,
Doreen

https://www.hondapartsnation.com/oemparts/a/hpe/50f73602f8700233e4c92f04/front-wheel-1

replace nut on inside of deck with a self locking nut. take bolt & nut to hardware store & tell them you want a self locking nut to fit bolt.

https://www.hondapartsnation.com/oemparts/a/hpe/50f73602f8700233e4c92f04/front-wheel-1

replace nut on inside of deck with a self locking nut. take bolt & nut to hardware store & tell them you want a self locking nut to fit bolt. a self locking nut will have hard teflon at end of threads.