There might be a lot of
that sort of thing going on, but there's also much of
the opposite. Either can be smart or silly things for the characters to do. And the characters probably don't have enough information to realise which is which.
It's how it's written, and part of how it is written is whether there's an experience (direct character expertise or an "oh no... I've seen this kind of movie before" kind of awareness) to have them be genre-blind, genre-savvy or
wrong-genre-savvy. And when it's something they might never have expected (that inconveniently shorted circuit was due to Snakes! On your Plane!), you can excuse characters wandering around on their own before they know they're going into danger. And even when they have the initial inklings because they still don't know enough to be Afraid, Be Very Afraid, or consider time-restraints the more vital pressure rather than needing to double[1][2][3]-up at all times.
Then, once it comes to "Ok, gang, we need a multi-part plan to get us to safety and/or negate the danger", there's not likely to be a sit-down meeting with flowcharts and full risk-analysis to cover each and every way in which the still somewhat mysterious nature of the antagonist(ic element) could derail individual or group survival. Military-trained practical awareness (or encyclopædic knowledge of the entire ventilation system) can only go so far.
[1] Not that doubling up totally works, as a pair watching each other's backs are still often enough picked off as essentially two singles due to inopportune separation or momentary inattention/misdirection by the first one to succumb.
[2] And if the danger isn't known/assumed to be one of the party, in which case Tripling-Up would be advisable, to prevent easy backstabbing then the rogue element fakes their death/their partner's complicity in order to then start to pick off other pairs at leisure.
[3] It's so easy to over-(/under-)think these things, and get the balance wrong for the situation. Character flaws might help, but the simple lack of omniscience might just be enough to make a few ultimately bad decisions from.