Sorry for the delayed response. Haven't been on the forum for awhile.
I found the problem. On the outside of the rig at the incoming water selector panel, I unscrewed the face plate so I could get to the fittings behind the selector valve. Sure enough, one of the Pex fittings was loose. After undoing all of the fittings, putting teflon tape around the male fittings, and screwing them back on tightly, no more leaks. What was happening was the incoming street water was dripping from the fitting, sliding down the tubing, and dripping off onto the floor under the shower stall. The illusion was the leak was further inside, showing up under the vanity. Hope this helps.
Stu