Thank you for the feedback, since your comment we've gone back and checked the walls, and apparently that wasn't the only one that needed fixing
To go through the vent you need a gnome of matching shapes, but the hit box works weirdly with perspective, so sometimes it will look like you can enter a vent while you cannot. Prompts were originally planned when you got close to an object that was interactive, letting you know you were in reach and what did they need (certain height, certain gnome shape or item). Sadly, those didn't make in time to the submission.
We definitely agree with the credits part, the credits sequence, it was an oversight