Back in my early working days I was called to a customer's factory to sell them a new paper cutter. I thought I would be selling to an in-house printshop. My jaw dropped when I stepped into a giant room where HP made it's transformers and coils, and found hundreds of ladies at tables spinning fine wire around cores, separated by long strips of brown paper. Capacitors, coils and transformers are delicate constructions, and the hotter they run, the shorter their life is.
After some frustrating issues I made it a practice to replace coils right away with new ones or, better yet, performance coils from Accel or whatever. I would think current coils are better quality than I experienced decades ago but maybe not. Chris