Goofs

The doors to the stairwells of the relevant section of the power station open toward the stairwell, via crash bars on the corridor side and via handles on the stairwell side. When Water and his two companions exit into the stairwell and rush down the stairs to the ground floor, they find that the handles of the door there will not budge because they are locked. In one shot, they are struggling to get the doors open, then there is a brief cutaway close-up shot to one of them beginning to reach for his smartphone, and in the next shot, the doors that they are standing before have crash bars rather than handles. It could be that these other doors were along an out-of-frame wall, but even if that is the case, the children's positions relative to one another do not match the previous shot, as though an entire sub-scene (of them trying to exit through this new door) is missing.

The fact that not even the second pair of crash bar doors encountered (that likely lead directly outdoors) could be opened to allow Water and his two companions to at least escape the power station (even if they were to have still missed the bus) is a bit of a stretch. Even more of a stretch is that they are never able to leave the stairwell so as to get to a place where cell service is available. No explanation for these wonders is provided.