The brake assembly on a ride on mower is very important. It slows the rotation of the blades to a stop quickly when the lever is disengaged. It appears mine has broke off and needs replacing.
What I ended up discovering is a weld break on the mower deck.
Where the weld makes contact with the mower deck had rusted through. The only thing I could do (other than buying a new mower deck) was to attach a short piece of steel plate with a flat head bolt with a lock nut. Hopefully that will hold up for a few more years.