Your expectations were way too high. Even so, there are a ton of bad and good distributors. Stern’s quality control has always only been as good as it needs to be to keep the doors open. Becoming a distributor is extremely easy, especially if there is no one to compete with in your area of the country. It’s not like buying a new car. It’s not like buying a new stove. It’s not like buying a new TV. It’a a lot more like buying a swimming pool. It’s never going to be maintenance free and there will always be concerns and issues no matter who you buy from or what you do.
You should consider reaching out to Pinside members or other league/locations in your area that are extremely experienced with pinball and ask them what distributor they buy through. Unfortunately, pinball manufacturer’s profits are rarely spent on quality control, customer service and distribution. Sad fact is that they don’t really need any of those things to work perfect to sell ultra expensive toys to pinball nerds. Just pump out the next piece of $7K-$10K candy and it flies off the shelf until it’s sold out. Even if it’s a flop, they sell enough of them to at least break even. This is all carefully calculated and decided before a game license is even secured. So sad but so true.