system shuts off then comes back on

my system recently started switching off (head unit and amps) and comes back on after a while. once back on I have to reprograme the head unit. this happens all the time. I had the battery checked. all power, ground and remote wires and connections checked. head unit send back to dealer but no fault found. other head unit tested in car with same result. system has been working fine for about 13 months without problems.  car: toyota tazz, 2005 model

setup: head unit: rockford ravdvd1, 7" audiovox screen, two targa 4 ch amps, one targa mono block, one farad power cap, power and ground cable size is 4 gauge, 2 fuses at battery and 4 at distribution block

Sounds to me like a problem with the headunit constant power supply, my suggestion is running it directly to the battery with a fuse inline and seeing if that solves the problem those A/V screens are pretty power hungry and the wiring in the harness may not be sufficient.

-->Richard