I found water leaking from the underside screws, closest to the jack, on the bottom of the rounded molding on the driver's side of my camper. It's the molding that they add last where the wall meets the overhang.
It turned out to be rainwater ran INTO the water heater through the door, and was then channeling through the incomplete silicone sealer inside the water heater's door. There is a bead that is added between the door-hinge ring and the inserted body of the water heater.
The camper tilted slightly forward when loaded, so it ran through the channel's underside and pooled at the jack.