Wow, that's bad luck.
The measurement of the antenna/ground is as expected - it is a DC short, but RF passes fine.
The measurements I would take first are some voltage and current measurements.? The current measurements are particularly instructive:
1) Power supply voltage.? If you can vary the voltage, set it to about 7.5V for the remainder of the measurements.? If you can set a current limit, set it to 250mA.? This will avoid any potential further damage.
2) Power supply current with QMX powered off
3) Power supply current while pressing power-on button
4) Power supply current after releasing power-on button
?
Also read the 'startup' page on the Wiki so you know the sequence of events as power is first applied to QMX:? /g/QRPLabs/wiki/36878
All of the above data will help you communicate the details of the problem to Hans, and to you and us if you want to try and fix it yourself.
Stan KC7XE