That was where it needed to stay if it was going to work for me, and they really botched that part in my opinion. The most compelling angle was the psychological "horror" aspect of co-existing with people they don't know or trust, all the nitpicking of details and stories to try and suss out the truth (and then what to do about it) is a tight story you can tell in a bottle and works because people go crazy.
The moment they leave the house and then end up coming back it's like the film just released the valve on all the pressure they'd been storing up and doesn't get it back. It doesn't really become much of a character conflict or a shift in the balance of power, the homeowner is basically just like "oh hey guys, welcome back, shame it didn't go well" and leaves the matter essentially settled, but everything afterwards was less compelling
It's got the template of 2-3 different stories but they clash with each other in a way that left me feeling like they didn't really tell one at all. It's got LOST vibes in that way, there's stuff for your brain to chew on with these individual premises but not enough time/ability to tie it all together, so as you approach the end of the runtime it doesn't feel like you're strapped in for the ride so much as watching from the outside trying to keep track of X, Y, and Z from earlier and put the parts together in a way that is satisfying. That's a shame, because the film should be doing that for you and it's not like this one is lacking interesting premises and visuals.
I'm also willing to hand-wave a lot of stuff when I'm having fun watching something, but when I'm not I start really noticing things like a man being incapable of seeing more than about a foot in front of him until he's standing in a plane crash (and other visual/direction decisions like that) or the kind of crazy decision to go get magic un-sick pills for a mystery illness, and those started to pile up.
edit: I watched a recap video to make sure I wasn't missing something obvious and way too many interviews with the director and cast are answered with "well that's really open to interpretation" and I get wanting room in your art for commentary but this isn't a choose your own adventure film, that can't be the answer to a lot of the questions.