Regarding reliability issues: I don't know how you would measure this, how you would determine this, regardless of where a bike is made.
Me, I had an engine failure on my '22 C 400 GT, after c. 5,000 miles. But I've read about assorted failures of many of what I think are the NON-made-in-China Beemers, too, as I hang out on a non-scooter BMW bike forum, too.
And you can read about failures of pretty much any bike, on its respective Internet forum. Hey, that's a large part of what forums are for: to report issues, and maybe see if they have happened to others, maybe someone has a fix, etc. You don't see a lot of "My bike has been working perfectly for five years and 50,000 miles now, no issues." Not a whole lot of incentive for folks to write those kind of posts.
I suppose if you had a JD Power survey for bikes, or if Consumer Reports included them in its annual surveys, you might learn something useful.
In terms of other scooters, I've owned two Burgman 650s over the years, and the bodywork seems much better designed -- how it's put together -- by BMW than by Suzuki.
What I find most annoying about the C 400 GT is not a reliability or a quality issue, but rather BMW's failure to include TPMS (and its preventing an owner's adding that, via its stupid sideways Schrader valves) and cruise control. For European and Asian markets, it's hard for me to see why someone would buy a C 400 (GT/X) instead of, say, a Zontes 350 E Maxi (see, e.g.,
www.youtube.com/watch?v=RdMQjd6OKHs ), which is much cheaper and has a bunch of additional features.
The reliability seems okay to me, and I love the styling, handling (absolutely superb), braking, and pep of the C 400 GT ... but it's lacking in a lot of other ways. Still, here in the USA, it's one of the better picks -- perhaps the best -- in its genre ("almost-maxi scooter," if I may invent a category name).