Sometimes it's a mixed bag when it comes to construction quality. I've had very few problems with any of mine. I think an NX nacelle arrived detached but it friction-locked easily back into place. You could call them to get a replacement or you could try resetting it yourself with superglue or JB Weld.
It actually helps that the collection is so big, I know beforehand I'll not be able to get them all anyway. My solution so far has been to clear a shelf and allow myself as many purchases as there is space on it. I'll likely max out at 15 or so, so I have to be picky.