Quite honestly when you are paying that kind of money for an engine you expect better service. Yes, I realize that Lionel and MTH are not big companies and all the rest and they either don't have a service department or what they do have is warranty only and undermanned, and yes it is the way they run...but that doesn't mean customers should shrug this off either, Lionel and MTH aren't charities and are selling a premium product at a premium price.
One comment caught my attention:
'There is going to be natural build variances in each locomotive. No two locs off the same production line are 100% exact. Its called build tolerances."
No, it is called poor quality, period. What you are saying was the problem with craft production, when you didn't have interchangeable parts and a craftsmen made them (the idea that hand made items are better than assembly line in terms of quality fails in this regards). The whole point of interchangeable parts and especially now with the techniques of lean production is that tolerances are supposed to be pretty much nonexistent (ie instead of saying the hole that the truck fits into should be .1mm to .3 mm in width, it pretty much is it should be .1 mm). What you are describing is not modern manufacturing, that kind of variance is craft building level of quality. That a truck is so loose it can come off (even if it is supposed to) in the box is poor quality. That kind of thing is what almost killed things like the US auto industry, GM and the rest thought like that....
It isn't the customer's duty to fix things and to expect them to on a routine basis is ludicrous IMO. That said, I think it also tells the tale on these products, that this is not an occassional thing but rather that people are saying "When you buy them expect problems and you need to learn to fix them".
On the other hand when you have 0 competition and if you want something nice you have no choice, that can be the reality, learn to fix it yourself or hope that 6 months after you bought something you might have a workable product *shrug*. I would talk to the dealer and see what they recommend, I realize it isn't their problem but they also have a vested interest because if you or another customer gets angry and doesn't buy, they don't make any money either. Sadly the dealers have little to no power with the manufacturers either likely, but maybe they know something.
As someone who knows how quality works, it makes me sad to hear that a modern product has that kind of problems. Yes, a let of people say they bought new engines and they were fine, but the fact that people talk about what they routinely have to do when they buy one of these tells a different tale. There is a saying I use when testing software, that if you are looking for a needle in a haystack (which is what software tests should be looking for), and 5 needles jump out at you, chances are there are a lot more hidden in that haystack.
All I can do is wish the OP well, that he gets some kind of resolution. It is sad that in 2022, when we have cars that last 250,000 miles, when while tv sets have gotten ridiculously cheap they last for many years and are generally good quality, people have to put up with this from something so expensive. Reminds me of people who bought Mercedes Benz cars before about 20 years ago, was much the same thing.