Troubleshooting Advice/Ideas

My damn stereo has been screwing up. I bought the truck with the non-nav system and then bought a OEM nav one. Later added amp, speakers, sub. A couple of times over the last 2 years it would do a weird thing where one channel (usually right front) would cut out then work fine, then cut out etc. I troubleshot to no avail then tried disconnecting the battery. That seemed to reset it and it worked fine for months. It did it again and another battery disconnect reset it for months again.
Now it's been doing it, but switching from front left to front right. Sometimes fine, sometimes no left, sometimes no right, and sometimes a few crackles and pops. The battery disconnect has done nothing (tried a few times) and considering the battery disconnect used to work, I assume it's the head unit.

So, my plan is to reinstall the original non-nav (if it still works after 5 years sitting in a hot storage shed) and see what happens. If all is good then I know it's the H.U. and decide to look for another OEM or an aftermarket one. If not, I start looking at the amp.

Any thoughts?

Oh, 2014 SR5