Electrical – I have a curious problem with the home electrical system that may come from the on-switching of the refrigirator or the freezer

For the last few weeks, from time to time, the line voltage as measured with a good AC-voltmeter, would drop suddenly from about 127vac to 105vac, and would stay there for few seconds and then would get back to about 127vac again, or would go to 110vac and stay there for a long minute or so before going back up to 127vac or staying there a few minutes longer. When this happens, if I use a 1100-W microwave oven, the oven would light up and turn the tray, but the food to be heated would not be heated at all.

It happened that something interesting was chanced upon: If during a moment of this voltage sagging that made the room lights dimmer, I turned on a cloth dryer in a distance away or a resistance little oven nearby, the lights got bright again as normally observed before the trouble. At that time, if the microwave oven is used, it performs perfectly OK. I took time out to measure the line voltage of that OK moment and saw the 127vac level being there until the end of the on-time of the cloth dryer or the resistance oven.

I have been playing with home AC circuits, electronics and computers since the age of 12, and have a BS, MS and PhD in power generation, distribution, conversion, industrial and communication electronics and computer hardware design and software, and owner of 8 US Patents. Yet, I cannot have an instant answer to this problem.

Can anyone have the same problem with solution or have some good idea be kind enough to let me learn from you to deal with this problem in a neat and safe manner. My house was built in 1914, but the central circuit box apparently was updated sometime in the past 60 or 70 years before with many of the outlets in the 3-prong configuration, with practically zero-volt measurement between neutral and ground connections. All circuit breakers at the central box look like standard 20A or more breakers, without any modern-looking appearance of Ground-Fault-CI or Spark-Fault-CI. Thank you in advance for your advice.