Thanks for all the suggestions, gentlemen.
Nick - Yes, in command mode with all handles forward and without being addressed, handle A is at 0.2 V, handles B and C are at 18 V, but handle D is at 18V (and can't be changed from this). Handle A responds as expected with the Cab-2 remote, but only reaches 12 V as the maximum. Each Powerhouse is outputting 18 V, as checked at the Molex connector.
George - I was able to reprogram the ZW-C into conventional mode by assigning it an TR ID of 0, so now handle A comes up at whatever voltage the handle is set on. I retested again with my Legacy engine and it still won't run even in conventional. The Legacy base is off and unplugged from the outlet and it is detached from both the ZW-C and track. I wired my track into handle B (not A) and am trying to control it from B; as soon as I turn on handle B's PowerHouse, the engine's lights come on and its sound system activates, but the handle is in the off position. When I raise handle B, the engine's bell starts dinging and it continues to sit there. If I cycle the handle from off to max repeatedly, the engine appears to be cycling through forward-neutral-reverse-neutral judging by the reverse headlight lighting up, and sometimes the engine will move forward, but the bell continues to ding (occasionally it will randomly turn off/on while moving handle B), but I can't seem to rationally reproduce the behavior and the cab light flickers on/off like track power is being interrupted, even with the handle at full. You'll recall that handle B does not have a bell button, so the observation that it turns on immediately and I can't turn it off has me suspicious that there's something wrong with a board inside. My multimeter reads ~18V at the track when the engine is sitting there dinging its bell.
