It looks like something was intermittently arcing and causing both the voltage fluctations and creating lots of EMI that disturbed the electronics. I agree with the others here that it doesn't seem the problem has been fully fixed, and a "lost neutral" could be the ultimate problem. Unfortunately these days it's rare to have incandescent lamps which will very clearly show a lost neutral by brightening as the voltage goes up, and a lot of electronics have universal input SMPS which will be fine with 85-250VAC.