I have a similar problem with the power company. Every day starting around 2200 (excluding Saturdays and US holidays), there are irregular voltage fluctuations in the 118-124 voltage range, which cause really annoying light flicker and might be damaging my appliances (3 water heaters, 2 microwaves, and an air conditioner all dead in the last 5 years), some of them new. It affects other neighbors and is clearly coming from the grid.

Repeatedly calling support (which initially was promising, since they had an engineer look into it and replaced the transformer and ran a new service entrance cable when I upgraded my load center [400 A service, and cost me about $12,000 but I was desperate]), simply led to me probably being marked as a nuisance customer. For all the same reasons listed in the linked article, they simply aren't equipped nor motivated to do anything about it.