Camilo Ramos wrote:
When repair guys have been at the house the lights have
flickered noticeably, even wiring their transformer directly to the
breaker panel.

Suspect the main circuit breaker and associated wiring.

Try to find out how many other houses are powered from the same
pole transformer as your house. Borrow a welder or other heavy
power user and confirm the flicker at your house. Try it at
other connected houses. A flicker at your house with a load
at a different house indicates a voltage drop problem at the
pole transformer.

--Winston