Does that system use an orbit valve with no mechanical linkage from the box.. or does the box have a sector gear, steering arm and a draglink that manually actuates a valve on a steering cyl.
If the latter, sector backlash and thrust bearing tolerances may be opening up in the box, and the rod ends in the draglinks may be loose.. all that adds up to alot of rotational play in the wheel with no wheel action.
Alternately, play inthe spindle bushings, and pittman arms and steeirng draglink ends will do the same. Worn linkage at a steering cyl control valve will amplify all of these.
post back with more details.. I'm not familiar with cub cadet models and options.
If it is an orbit valve.. I'd guess many of the passages may be plugged.. perhaps a hose or filter came apart internally.. that happend to me once on a piece of heavy equipment. took hours to use a piece of fine wire to clean all the hose fibers out of the plugged orbit valve..
soundguy