I discovered that the downstairs bathtub had improperly cut tile, leaving a gap for water to get inside the wall behind the shower controls escutcheon plate. The trim kit will have to be removed, the faulty tile carefully taken out, and a new one cut to take its place.
I also learn that the master bedroom walk-in closet, rec room closet, and laundry room dipwire shelves are not attached to studs. Instead, they are mounted with flimsy plastic anchors that easily tear out of the drywall when weight is put on the shelves.
Additionally, a downstairs storage closet had handles installed on the wrong half of bi-fold doors.