So irritating

Our new clothes dryer has started to make noise while drying clothes. The clanking/clacking has become increasingly noisy over the last couple of weeks. I called to get a service person to look at it as it's under warranty. Wouldn't you know, as soon as the repair person came, it stopped making the racket. I tested it just before he came and it was making a racket. The guy was very accommodating and he took the whole thing apart to inspect it. He couldn't make it do it again. He said this happens to him a lot and not to worry. At another customer with a similar complaint he replaced a couple of rollers and a pulley and it seemed to fix the problem. So he's ordering the same parts and will be back. Just did a load of laundry and the dryer is quiet as a mouse. So irritating....