So the running cylinder has the low compression? That’s odd. I’m going to take a wild guess, worth nothing. A serious water ingestion problem into the lower cylinder, from either a blown head gasket or a holed exhaust cover baffle plate. Problem with that theory is it wouldn’t be “dry” as you said..
Hint: take a look at the edges of the exhaust cover, where you will see the two gaskets with a plate between them. If that plate is thin, like about a credit card’s thickness, that’s good. But if about 1/8″ thick, that would be one of the troublesome aluminum plates that corroded through.
