There was a similar problem at our entrance. In the evening, when loaded on the network, the voltage dropped to 185 volts. I also thought about the stabilizer. But an active neighbor managed to find a malfunction and they replaced the switch in the basement. After that everything came back to normal.
Therefore, it is cheaper to find an evil neighbor with free time, scare her with the fact that in this state of the network, her refrigerator will crash (which is quite likely) and sneak on the electricists of the MUZEP. The evil neighbor is a terrible force.