A bad neutral connection somewhere in the building or all the way back to the service entrance could cause that kind of a problem.
As they say always meter your power......
I had a job earlier this year that has been an annual event for years, same building, more or less the same system.
Check the couple standard 120 outlets I always use and find the voltage is swinging upwards to 138 and down to 100 or so, other outlets around the building that I check are doing the same basic thing.
Ask the people with the building if they have done any electrical work lately and told them the problem, they look at me and say they have been having issues in the entire building with everything electrical including their in house sound system, things not working right to all out damaged equipment.
I find out this has been going on for about four months!!!!
I tell them I can not power up my system till this is taken care of.
I still work on getting setting up, they call in their electrician , he finds the same thing, I tell him my gut feeling is a bad neutral, he's thinking the same thing.
Electrician finds a corroded buss bar in the outdoor service entrance panel, does an emergency repair and later changed out the panel.
I caught the problem earlier enough the event started on time!
