I have been looking for the same thing but haven't found anything like a scene replay functionality for story scenes.
Make sure to hide in the one track pathways, it's worth it to tank a bit of hypnosis to really get in there and hide away from the patrolling dark pools.
It is really working, the game now runs much smoother and I have not had any game breaking bugs on top of that. Altough locations in mad school door (and in less degree goblin nest) still can be laggy, at least after you apply this method it will be not THAT unbearable, location right after the infirmary with surveliance cameras is the only most FPS-heavy, so you need just to bear it a little and everything else will be easier. The only major problem I witnessed is that there are sometimes moments when FPS stutters when someone else's standing image shows up, when Rui's standing image doing some rapid movements (or someone/something else) or when there are some special effects going on screen - but again, maybe these were in game initially, or I had these stutters because my laptop is very old, so everyone else with better PC probably won't be having those issues. Shortly, I also recommend this fix. Just one thing - paste files from archive in "data" folder, where Game.exe is located, not where "-after mini-.exe" is.
