That is a solid mower and aside from the stump would otherwise run for many hours. I would try to straighten the crank or tear down the engine and replace the crank.
i,ve straightened a few of those cranks, i usually tip it on its side and pull the cord to check for runout, they are popular with uk contractors, and are $1.5k ish, so well worth repairing
update: finally tried to straighten the shaft, unsuccessfully. decoded to not invest any more repair time into it. however, i'm going to slowly part it out. popular mower, many out there.