Well, the trailer has been at the shop for almost a week. So far they have been unable to reproduce any dripping or noticeable leak. They started by putting water in the fresh tank and running the facets and pump. Nothing. Next I suggested filling the black tank. Which they've done, both gray and black tanks are 2/3 full. Still nothing.
I also suggested putting the nose up a bit, in case the leak just wasn't working down to an exit point.
What the heck?
He did ask if it was possible that I overfilled the fresh water tank when we camped that time. It is possible I suppose. Is there a scenario anyone can come up with that matches these circumstances? Is it possible that the drip was simply run off from overfilling the tank? It got stuck in the underbelly and eventually dripped out? If so, why the pungent smell of the drip? Why the smell from the vent?