please, do something about that install at the same time - what the hell are those additional rca wires doing there? the ground seems taped to something else? before you junk the amp, do the install properly, also check you amp remote to make sure it's well secured as well and that is has not come loose from where the other amp is connected - aka, the amp remote is coming on and off for just that one amp.

if its hitting protect, that's generally from a overheat or from an impedance issue. since it's just cabin speakers hooked up to it, and they all function properly when the amp is running, I don't see any issue there - or it's just a blown amp....