Do any of the neighbors possibly possess heat pump(s) that have a failing compressor or compressor start components?
I did run into this exact situation several years ago, and found that the next door neighbor had a heat pump that was trying to start and locking out. It only happened in the evening, after they got home from work and turned the thermostat up. They didn't really know they had a problem, as the resistance backup was covering the load. I heard the thing groan and snap when I was outside looking at my customers' meterbase.
