If you mean these two doors:
The blue-ish one (the door on the left) should lead you to the next scene, so it's very likely that it bugged for some reason, sorry for that. The problem should be fixed by reloading the scene or playing again from where you left off (Select scene in the menu).
It's probably one of those one-time bugs, so (probably) it won't happen again.
I'll take into account what you said about the monster placement tho. I get what you're saying, and while one encounter from the last scene does try to improve this, I think I can add some more dynamics to some combat sections.
Thanks for the comment, I hope you enjoy the rest of the game ^^