Loose Wires/ unreliable connection of wiring harness/ Need help

Gmax 1.5+
Having severe problems apparently due to a poor connection of wires inside the 'control' box.
Initial symptoms included a 'MINTEMP' error on the LCD screen. By wiggling the outboard wire harness/ bundle and restarting, this error would go away, machine would power-up, and print functions would become available.
Recently, any vibration to the table or printer (including printing function/ bed movement) would cause the printer to completely shut down (NO power/ blank screen).
Now, after some more wiggling of this wire bundle, the printer will not turn on at all. Just a quick flash of light to the screen and at the print head, followed by nothing. (no power/ no start up).
Seems evident that there are disconnected wires. This condition existed day-one, the first time I turned on the machine. It was tolerable for a while (about 20 prints), now the machine provides nothing. Flatlined, so to speak.
I'm reluctant to open up the box without some guidance. I have no idea what to look for, (other than loose wires), and no knowledge of what to be careful of, etc.
Thanks in advance for any help to get me running again.
We've become dependent on this machine for our business.