My daughter has an old home in pittsburgh. the electrical panel is probably 40 years old or more. We had an electrician add a 220v breaker for her clothes drier and that was the only change.
She has various circuits in the house that go dead. I had a handyman check all the outlets and switches. he repaired a few but didn't really find anything. The issue he had was that the circuits were working when he was there, so it made it hard to troubleshoot.
i visited her when they were out and when i tested the output side of the breakers i found that several were dead (no voltage to common or ground. All were in the on position.
to my surprise, when i had her turn on the dryer, not only did it work but all the other circuits regained power. Even afte the dryer was turned off, they remained on. they have gone off several times since and again, all come on when the dryer is started. I should have taken a picture of the panel but didn't think to do it. I realize that might help solve this.