When I had a loose cable connection at the HC or Gemini unit mine used to reboot a lot so maybe spray some DeoxIT or other on the cable pins and reseat them a couple of times.
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My test for cable seating was to start the unit with the HC sitting on something solid and see if it comes up OK - then pick it up and see if it stops working or reboots.
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The next step for me was to open and check the HC internals but I expect you will get some more experienced advice from others.
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Good luck
