Any film that establishes a rigid set of rules, or features a massive recurring element that can reasonably be accepted as irrefutable internal logic should have a pretty easy writing process. The writers need only remember those rules, or that one thing that needs to be adhered to, without messing, and they can pretty much do whatever they want: in some ways the structure should be seen as a plus point in fact, especially in a franchise where diverse narrative rules can be as hard to keep track of as multiple, childish lies.
So, you'd think those writers would just write their rules down on a post-it and stick it next to their computer or something, which clearly doesn't happen all the time, since so many rules are flagrantly broken in movies - sometimes within mere minutes of their establishment.
The long and short of it is that writers really don't care that much - spectacle trumps logic, and as long as not too many people notice, they will wilfully smash their own rules and logic into the floor for the sake of a few cheap thrills or a pleasant, easy resolution.
And the problem runs deeper than you might think...