MakerBot Print is our newest print-prepration software, which supports native CAD files and STL assemblies,
allows you to interact with all your printers via the Cloud, and many other exciting new features.
Sorry it took so long to reply. My printer at work is under maintenance and I had to throw my spare time there. Funny what one fan in PSU, that is not runnig, can cause.
Your understanding is correct. It is groungind elsewhere. But that results in unpredictable behavior and overload of some other parts, that may not survive it in long therm. The easiest way to correct it is to ground it as it should be done. So rather don't put any good parts in it unless you will find the cause or you may just loose more parts on the way.
I found one spare RAMPS at home and Arduino Mega is on the way from China. I will need it anyway as right now my ToyREP is not working (it was disassembled to give parts to other printer). Than I will be able to show you, how the electronics shall work.