It could be that your power line voltage is too low for the PCM70 to function reliably. The PCM70 monitors the line voltage and automatically shuts down when the voltage level falls 20% below the nominal line voltage that the unit is set for.

Possible solutions? You may have too many devices plugged into a single circuit, drawing too much current and pulling down the voltage. Try turning off several devices and see if the problem goes away. IF it does, then the circuit is probably overloaded. Either permanently reduce the load on the circuit or have an electrician install a heftier circuit.