Theory: Carol is blocking the player from leaving Hometown
I think Carol, working with Kris, is deliberately blocking the player from leaving Hometown.
During the festival, we learn the police tape's been replaced with a new one. At this point, Undyne's held in the shelter, and idk if Napstablook can, like, hold things. So if not the police, the most likely candidate for replacing the tape is probably the mayor. But why would she do this?
The entirety of Hometown is confined. The trees are very tightly packed. The only exits are the pathway blocked off by tape and the lake (and we've seen where that leads). And not only is it confined, but it's completely isolated from the outside world. The internet was recently cut off. Tenna's only playing reruns. Alvin's been receiving condolence letters for Gerson until recently. So, what's going on?
From Chapter 4's Holiday manor segment, we can piece together that Kris and Carol are probably working together. I'm guessing the reason her voice sounds different over the phone depending on the route is that, when the voice box is jagged, she's actually in the shelter. And we've now gotten confirmation that she's been "investigating" in the shelter. I'm not sure exactly what they're working towards, but we can assume it involves the Knight in some way.
Something else we learn in Chapter 5 is that other characters can go places the SOUL can't. This whole time, I thought the lake was deep and on the edge of a cliff. But, no, Susie just walks into it. She also just walks through the spikes. In WR, Noelle has to walk Kris into the lake. In NR, Ralsei has to walk through the spikes. From this, we can understand that the SOUL has to abide by certain rules. And I'm saying the SOUL specifically, because Kris can go through windows and other pathways that they can't access with the SOUL.
I'm sure Kris understands this rule, and if they understand this, wouldn't they tell Carol so they can use it to their advantage? During the festival, there are very conveniently placed obstacles blocking the way to the shelter where Carol is "investigating." Maybe it's just classic video game blocking, but if these two know about the SOUL, are using it for their plan, and understand its limitations, is it really far-fetched to suggest they might be deliberately restricting the player's movement? Hell, even NormalNPC does this.
Now, the real question is why. I think the first obvious answer is that they need the SOUL for their plan, so they can't have us fleeing from Hometown. But remember, Hometown is completely isolated from the rest of the world, and we've seen what happens when you traverse through the lake. You reach a blinding white light. I've been replaying Undertale and just recently reached the fight with Asgore at the barrier. And the barrier is a blinding white light. Given the WR themes of breaking the game, breaking the script, and seeing what's beyond the map, I'm comfortable assuming the white light Kris and Noelle cross in the WR is a barrier. Not to mention, you need a monster and a human SOUL to cross the barrier. They meet the requirements.
I think Hometown's completely surrounded by the barrier. Even if you could cross the police line, you would find the barrier. And this would probably be bad if the player found the barrier, or even tried to cross it. Carol and Kris need you. They can't have you knowing too much.
And on the point of Hometown being within the barrier and cut off from the outside world. We're constantly reminded that we'll see Asriel next week. Toriel wonders if they should go surprise him early at college. But I don't think they can. I don't think anyone can leave, and I don't think "next week" is supposed to come. I know timeloop theories and "there's nothing outside Hometown" theories aren't popular, and I understand why, but I really like someone's idea I saw (wish I could remember who so I could credit).
This person suggested Hometown got cut off from the outside world and trapped in this barrier at the exact moment the connection between the player and the SOUL was established, when Gaster launched his experiment. I do think they had lives before, and that there's a world out there. Remember how Alvin said he's been getting letters until recently?
In the Mantle game, there are several examples of imagery where you have to cut through trees to get somewhere or get something. And there are two mentions of getting lost that I think are interesting. The first, of course, is "lost where the forest would grow, the children followed the pointed tail. The poor children!" Another is from the ARG.
If you answered "the festival" to the question "Where will it take place?", you got this response:
"Well, it was always going to be this way.
The only people that walk this path...
... are those who have their face so close to the road
they can't even see where they're going!
...
But, well.
If we're lucky, maybe there's a chance you'll still get lost along the way..."
That's interesting to me. If you go to the festival, you're following the script. But if you go to the lake and enable the WR, you're not following the path. Getting lost.
Either, in the past, someone went through the trees and got somewhere they weren't supposed to, or we'll have to do it ourselves eventually.
Writing this theory kinda got away from me… I think all of this connected, somehow. Maybe I'm reaching, and it's all just regular video game blocking, but plenty of Deltarune's elements have been proven to be diagetic. And I think this would be cool.