Black screen at specific location

Well, you have the right idea! This is a power issue at the persons home.

They will need to get an electrician in to fix the buildings wiring. The problem is one or more outlets are mis-wired so the ground side is tied to the hot leg. So if the outlet is used the device plugged in is shorting the neutral side (now hot) to ground. Depending on the device there can be enough resistance so its not a full short, but the wiring and the device can get overly warm which could start a fire! A direct short would blow a breaker.

I would strongly recommend the owner check >> All << of the outlets inside and outside using a cheap outlet checker as it only takes one to mess you up! Outlet checker

The breaker panel its self could be bad or mis-wired! To add to this the buildings grounding services may need to be checked as well. The breaker panel should have a heavy gage grounding wire to either the metal water pipe leaving the building or one or more grounding rods, and the pipes or rods and the clamps are all clean of oxide buildup (Green junk) .

Even will all of this done one or more devices plugged in and/or turned on could be the source. Someone may have mis-wired a lamp or other device (three wire) or a transformer within the device is shorted out.

Clearly, this is not a system issue. You may want to recommend they get a good quality UPS to help protect their system, but thats not the highest priority.