Aren't they all sneaky?
I finally found one the ran down the inside of the driver's side front window. Fortunately I had a small bin on the dashboard that just happened to be located under the leak, and caught most of the water (~! inch deep). It was odd because the bin was about 1 inch away from the side window.
I discovered that the upper corner of the front cap had pulled away from the side panel just forward of the gutter, which allowed water to pour into it. There were also a few gaps in the corners of the fabricated aluminum window frames that needed caulking. I wish that a gutter extension was available, but the dealer was not aware of any that would fit.
Repairing it was interesting. I was on a ladder with a tube of black caulking, and I have a severe tremor that causes my hands to shake violently. What could go wrong? The neighbors came by to watch.