Is there a chance the head unit has gone bad?
Of course, but it's not likely. Pull it out & wire it directly to the battery to find out.
Instead of relying on the body ground as the return path, you could add a new heavy wire from the battery to several (or ALL) of the body ground bolts so that electricity can flow the whole way back in Copper wire. Make it heavy enough to handle everything coming in, which means it should be about the same size as the positive feed to the fuses & ig.sw. The best way to run it is as a daisy-chain; pull the long wire through the truck passing each point it will hit, connect it solidly to the battery (-) terminal, then strip it near the first point, fold it, & attach a good ring terminal (withOUT cutting the wire). Continue to the next until they're all tied together, and directly to the battery, and you should never have another "ground" problem because you won't actually be using the "ground" any more.
