Ink Maker wrote:
Somewhere close to your facility is using a lot of power
intermittently. Whenever they turn on or off a big piece of equipment,
they send the surge to every other users nearby. Since your building
will be torn down soon, a good UPS may be the best bet.

Back in the 80s with low end mini-computers we saw these issues a lot. Many times we'd find things like coffee makers on timers on the same circuit breaker. Or a welder next door but sharing the same transformer. Other times if we could establish the WHEN we'd have the folks spread out for a few days to see what might be going on. The most interesting one was a trash compactor across the street that was run at about 3:45 PM each day which is when the systems would act up. Turned out they were pulling down too much power and affecting the entire block.

David