Hog iPC controller losing power

I've been working on my iPC for the last couple of days, and the controller will lose power. The desklights go out, lights on buttons go out, and I get no function from any of the buttons or trackball. I can tap the face of it, and it comes back on and everything appears to be fine. What can we do to fix this? Loose cable? Bad solder? Do I need to send it in (I hope it is something you can tell me how to fix...)? Please let me know as this is a rental console as well.
Thanks!
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