Reason for today’s visit was to assess power loss in the living room receptacles as well as the front light switch. But initial inspection customer stated he was doing some work mounting shelving units on the living room wall. My first thought was that a screw had went through one of the wires possibly. After opening up the GFCI receptacle on the wall next to the freezer in the living room I found that the screws had not been tightened up very well which allows the wires to pop out of the back on the line side. I put the wires back in and tightened the screws up properly and power was restored to the circuit. Inform customer consider replacing remaining devices in home that were original were older as he could have power loss issues again with some of them all devices. The GFCI that caused this issue appears as though it’s been replaced within the past few years but it was not one we had put in.