Dead infotainment system

I’ve got a 2014 LS. I bought the car 1.5 years ago. Shortly after I bought the car, I started having problems the negative battery ground cable. The car would randomly not start once turned off, the ignition switch would not completely return to the off position and the infotainment system would stop working. I had that fixed and everything worked fine for a while. The infotainment system started to randomly flicker and then eventually quit altogether. Now, it randomly works but only briefly. On Star doesn’t work either but the On Star button blinks when it is pressed. Bluetooth is still active when the ignition is on. I’ve replaced the negative battery cable, again and checked all of the fuses, took out the button panel, the radio unit, display, the module under the radio and all of the wires and connectors appear to be good. If I leave the battery disconnected for a long period of time, it will come on for a few seconds but then it quits.
On an unrelated issue, the car thinks it’s over heating when it isn’t. The display will say “ac is disabled due to high engine temp” and the cooling fan continuously runs until it clears on it’s own. I’ve checked the wire connectors on the temperature sensors, on the fan and all appears okay. The water level and coolant is normal.