That might seem to be the most likely culprit. However, unlike descriptions I read online, the plants don’t wilt: They behave like they have some sort of plant gangrene that moves up from the lower stem, and the stem once affected appears to mostly dry out. The top half (3/4, 1/4, whatever is left) looks reasonably healthy, it’s just “static” (other than fruits dying almost as soon as they form) until the dying / drying gradually consumes the healthy portion from below. Somehow the “healthy” portion is still receiving just enough water and nutrients from below to hang in there. I was even thinking of taking a cutting and trying a “restart”, although I’ve never successfully rooted a cutting from any plant of this type...