This may or may not be related to your problem.
Here, on very hot days, typically around 5PM when all workers are returning home, the local utility company intentionally reduces voltage (as much as 6 volts). This is a brown out and they do it to reduce the load.
We have 50 feet of cable also; this further reduces our voltage. We have seen the voltage as low as 110. I panicked the first time, thinking there was a problem with our rig. Two hours later, when the sun went down, the voltage returned to normal; the power company had resumed full power transmission.