We've resolved our issues with some modifications. First, we had the outdoor sink removed and a new counter top installed. All the associated plumbing was capped off. Still we had water infiltrating the enclosure and it was apparent it was from above. Turns out the top of the outside kitchen door was letting water in whenever it rained. I don't know if it was the hinge, the seal, the frame...but I do know that silicone caulk didn't seal it. The resolution by my new favorite RV serviceman (Wayne of Abe's RV Service in Delaware) was to fashion a flange and mount it over the hinge so that water is diverted over and around the door. It has been dry inside now for many weeks and - as long as I don't leave the door open while it's actively raining - I don't anticipate any additional issues. Thanks, Wayne!