Mysterious Collapse of a 7-Foot Pachycereus marginatus After Moving

A 7-foot Mexican fencepost (since 2002) turned black, split, and dried within a week of a 1.5-block move. Movers noted "small accident." Rot starts long before visible—overwatering months prior, or move trauma. Ohio grower: monthly water May–Sept, half Sept, none Oct if moist, winter dusting only. 8hr lights, 63°F, 50–60% humidity. Rot started at top, went down. No cutting possible. Setup sounds good; cacti are unpredictable. Different approach: total water stop Oct, unheated dry room till March, summer outdoors. No schedule—water when bone dry. One of my cacti collapsed suddenly after looking perfect—rot started months prior. Check roots/tissue of dead plant for learning. Sterilize pot. Get a new cactus—you deserve it.