With a series spanning sixteen movies, several one-shots and countless hours of television, it would be virtually impossible for the Marvel Cinematic Universe to get away with zero contrivances, questionable plot developments or straight-up mistakes.
There are a few, all of which are fair to point out - the most recent example being Spider-Man Homecoming's absolute butchering of the franchise's timeline, which is quite bizarre to behold - but on the whole, given Marvel's keen attention to detail and their focused planning of movies that are years in the future, the MCU is as watertight as it gets.
But that hasn't stopped people pointing out several problem areas that would seem reasonable to argue at first glance, but after a closer look at the issue in question, aren't really problems at all.
Sure, the movies don't always explain everything in perfect detail, but that doesn't mean there's a gap in logic or a continuity-destroying problem. Occasionally, we'll have to dig a little deeper or think a little longer to find the answers, and that's certainly the case with the following ten points of contention...