I would check the bus where the breaker plugs on. I just repaired one that had the lights blinking and slowly going brown and then back to full on. Found a bad connection on the panel bus, same as yours breaker would not trip but you could reset it and cure the trouble for a while, sometimes. Breaker showed no arc markings, bus had slight markings visible only under bright light. You never would have convinced me that was the trouble if I had not been there.
