(1) At the university, we had a a laboratory with many computer controlled devices.
(2) In different department, there was daily use of an old elevator, daily, at odd times.
(3) At odd times each day, the Lab computer controlled devices would "reboot', killing data.
(4) Trouble Shooting:
By placing Oscilloscope on the feed into the lab, and monitoring for hours, and hours,
we determined that the elevator was pulling down, and spiking up, the feed on that side of building.
Only the laboratory computers were tricked into rebooting; very sensitive, and safety protected.
All other personnel in building recalled only a 'possible' blip.
(5) Point is, the problem was in an adjacent electrical load.
(6) Application is, perhaps a neighbor's residential electrical load is causing a spike / flicker.
* Also, incandescent lights seldom flicker
because they are thermionic (heat driven) with a thermal time cycle of aprox. 1/10 second.
* But, LED are run off instantaneous elecric power,
and their power-on cycle is 1/60 or 1/120 of a second, very flicker sensitive.
* Example: We have seen motion-detector-driven electronic-switches flicker faintly continually.
due to being loaded to the max wattage. The LED lamps in the long hallway flickered faintly, often.
These were 1200 W electronic switches loaded to 1200 W of LED lamps.