[sourdough]

Well, while we are speculating let me throw this out;

While at our mountain home day before yesterday I was working on the shower in our little guest cabin - much like an RV shower. When I had them replace all the plumbing in the building years ago they had cross threaded virtually every connection as it changed from PEX to the connections for the faucet and shower head - they leaked. I had no idea because we had not used the shower there since the lines were installed. Replaced all the connections along with the faucet. Turned it on and checked the hot side, then cold, then both....no leaks. Went around and turned off the faucet and looked back at the new connections - they were dripping; when I turned the water OFF. Dried it up, repeated the process and began leaking when I turned the faucet OFF! Don't get it but had to reseal/tighten all the connections to make it stop. It doesn't make sense but maybe you have some weird deal like that.