Your pto input seal is leaking. The easiest fix is to pull the engine. Replace input seal, flexplate, and "very important" the bushing in the flywheel, also a good time to put rear crank seal in engine. Check new bushing fit on your old shaft. More than likely your old shaft is worn where it fits into the bushing, causing the shaft to "wobble". Can fix with a new shaft, but that is a little more involved, I would recommend going to a machine shop and have a sleeve or undersized bushing special made to fit the worn shaft. Sorry to ruin your day, good luck.