Hello,
We have ordered 2x netPower 16P and they both put out current on the frame ground screw. It's the same voltage that's going in via the DC ports.
I am assuming that we did not receive 2 defective units and that this is the design. That being said, it's a bad design, since it pops our fuses all over the place and back feeding current into other devices via ground. There is the option to not use the ground, but that's not sane, if you know what you are doing.