Sounds to me it could be a bad clutch, that is if it has a clutch.

Yes, it has a clutch

You are going to need to adjust both reel and wheel drive clutches as they interact with one another. to do so, you are going to need both a conventional 1" open end wrench, and a second "thin" 1" open end. Commercially they are sold as "tappet" wrenches, but tend to get rather expensive. A less expensive alternative is to get an old piece of 1" iron from the flea market and grind the faces to make it thinner.

I have a 15/16 x 1" wrench where I ground both ends so I can adjust Tru Cut and Cooper Klipper and King O'Lawn. Basically you adjust by holding the main nut and loosening the locknut, and then screwing the main nut in or out to get the adjustment you want. When you are satisfied with both reel and drive, you then tighten the locknut while holding the main nut still. You may have to repeat back and for a couple times to get the adjustment you want.

BTW, most professionals adjust the clutches on a Tru Cut to have the reel positively engage (past the detent) but have the wheel drive adjusted to engage with thumb pressure and not to be positively engaged. This way if you release your thumb you stop. It's a matter of personal preference.

Should the reel be free spinning to finger pressure when the reel engagement button is fully disengaged, and the wheels able to go backwards or forwards when pushed/pulled? If not, does the reel clutch need adjustment? Wheel clutch was adjusted so mower does not move forwards on its own if wheel drive button is not depressed.