Not sure what I'm looking at there. Which way is up in that last pic? An open-ended tube is an air intake, or not used (sometimes scraps end up in the foam), but that does not mean that's the problem.
HS builds the tub then puts in a spray of soft spongy foam, often with voids at the "top" (it's upside-down when they do this), then fills with dense, closed-cell foam, trims the "bottom" and spray a plastic-like epoxy on it. This creates channels around the pipes, wires, etc, that hold and redirect water flow. Unless you see it drip from INSIDE that tube it could be anything, anywhere in that tub, tracking down the foam. I've tracked HS leaks to the opposite corner from where they showed.
Plug the tube and see.
