You can have compression rings that are still great but the oil control rings can be marginal.

You soaked one cylinder because it was low in compression. Then it went normal. Did you soak all the other cylinders? My thoughts are if one was stuck chances are some of the others may be partially so ring wise.

If not I would do that. The soaking again obviously loosened up something that was stuck. If the car has been on vegetable oil specially make sure they all get a good soaking. Probably about the cheapest thing you can do with some potential upside.

Sometimes the rings stick a little just from siting around. A container of miracle mystery oil added the the base oil of the engine will do no harm either in my opinion. It seems to be a powerful solvent.