If it was me I'd just pull it apart and start over. You'll spend more time dinking around with it than it it's worth. It could be a bent crank or it needs a line-hone. You can't find that until the rods are out of the way.
But my guess is the rings are dry.I have watched mechanics grease the skirts with white grease, which after the oil runs out of it, leaves the soap behind, which then cakes up.....
