DIAGNOSIS The wheel hub bushings are worn out, allowing excessive play between the wheel axle and the deck mounting bracket.
FIX Replace the wheel hub bushings. Remove the wheel by taking off the axle nut and washer. The plastic bushing sits inside the wheel hub. Pry out the old, worn bushing and press in a new one (Part Number 44611-VH7-000). Reinstall the wheel and tighten the axle nut snugly, but not so tight that the wheel can't turn freely.
IF THAT DIDN'T WORK The wheel axle itself might be bent from hitting an obstacle. Inspect it for straightness. A bent axle must be replaced.
HEADS UP Check all four wheels. Wobble usually affects the rear wheels first due to the drive forces, but front wheels can wear too. Replace bushings in pairs (both rears or both fronts) for even tracking.