Duo 2.0 Hotend problem

I'm wondering if this is a firmware issue, so would like some advice before I dive in.

Extruder 1 works as expected, but extruder 2 does not heat.

What I've done so far:
Updated firmware to the latest
Removed extruder and tested on the bench...heats fine
Tested thermistor...resistance checks out fine
Multimeter on extruder connection...shows voltage at ~12v when told to heat
Removed plug and socket, and soldered direct...no change

So it looks like the hotend and thermistor are fine out of the printer, and that the thermistor is working in the printer (if I hold the hotend while connected to the printer, the display shows the temp rising a few degrees). I have also confirmed that when the hotend is connected, that a short is happening on the plug end.

I've submitted a ticket to XYZ, but it could be days before I get an answer.

I tried the link to the wiki (http://http//www.soliforum.com/topic/636/hot-end-isnt-hot-how-to-repair/) but cannot access it, page unreachable.

Thanks for any advice here.
Paul