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I mean one example of the top of my head was:
They establish that: "It" is a creature/demon that always walks slowly towards you.
OK! Cool!
Well than you see a scene where "it" is just standing still (taking the form of naked old man on top of the house).
I need to re-watch the film but I remember all but there were at least 2-3 other moments.
Remember Superman comics and movies where sometimes he has trouble lifting a bus ( when the plot demands it), in another part he lifts an iceberg or something . Well I hate that. I want consistency! :)
That's what I mean with breaking the rules(consistency).

Thanks for the feedback, although I still think the lore stands up to scrutiny for the following reason:

I'm not sure if Hugh's explanation at the start ascertained if the creature "always" has to walk given that the adolescents themselves don't much about it. There was also another instance in the movie where the creature remains stationary for a brief period of time as you mentioned. In addition to the fact that the creature walking "all the time" simply couldn't work on a logical level *(e.g. obstacles, etc).

Nonetheless, interesting observation, bud. :)