Thanks for Choosing Just Answer.....
I do not think the ignition switch would be faulty as if that was cutting out you would loose power to the engine and ALL the dash functions. It does sound like a loose wire or bad ground. I would start at the chassis battery, inspect your cables make sure they are clean and tight and the crimped connectors are not loose. make sure the main ground to the chassis is also clean and tight
Next I would find the chassis fuse box check your connections and make sure the ground for that is clean and tight. IF you see an connectors that plug together make sure they are not loose, some manufacturers will bundle a bunch of 12 volt wires and have a male and female plug that will plug together, over time they can work loose....
I would also check the area where the main harness is going into the unit from the chassis fuse box and make sure it is not rubbing on the frame.
Issues like this are hard to pin down with the amount of wiring but it does sound like you have a loose ground or bad connection..