I came up with most of these myself, though not all of them. I think they're pretty funny, so I thought I'd share. Just a quick heads up, this is in the "the whole game is a movie or something" universe, and not in canon. Also, these are listed mostly in the order they go in the game.
The audio from the audio logs is said live for filming (usually by the person who’s in the audio log), then added in post; it becomes a contest among the cast to get Henry/whoever’s talking to laugh the most
The Ink Machine just stops halfway out of the hole
The changing picture doesn’t move at all
Henry dropping the objects multiple times; the inkwell breaks at some point
The mechanism for the Bendy jumpscare breaks and it just falls flat on the floor
Henry gets so startled by the projector turning on that he trips on the step and falls
The drainage system for the theater doesn’t work and the ink gets way too deep
Bendy accidentally breaks the boards when he reaches for Henry
Henry trips on the giant pipe in the hallway leading to the Ink Machine
The trapdoor doesn’t open, and the exit door isn’t made to be opened, so Henry just slams into the door
The axe isn’t where it’s supposed to be
Henry tends to break any instrument he touches, whether on purpose or by accident
The lights in the Music Department don’t turn on
Most of the searchers are just CGI so the any fight is the most boring yet hilarious thing you’ve ever seen
The giant stack of crates and barrels in the pool room collapses
The crew can’t remove the Bendy cutouts from the stage fast enough so when the camera pans over to the stage they all just freeze while holding the cutouts
During the fight on the stage, the crew tries experimenting with using real people as Searchers using a trapdoor in the set, but they told everyone except Henry, so when one popped up Henry fell back and broke a chair, then knocked over a bunch of music stands and the drum
The lever doesn’t open the door to the sewers
The chain for the pallet breaks and everything on it spills onto the floor. Wally and Thomas just sigh and start fixing it
Jack forgets his queue to sink down the first time Henry sees him, so Henry just grabs the valve and bolts
Sammy was the one who came up with the finger wiggling during his speech; the first time he does it the entire crew bursts out laughing
“Rest your bed, it’s time for head”
The rig for the ink puddle coming out from under the door accidentally goes off in the middle of Sammy’s speech
When he notices he just points at it and says, “That is me” and continues
Henry forgets to close the door after being chased so Bendy tries to go through but hits his head on the doorframe
Alice films it and turns it into a “Wasted” meme
Boris forgets he’s supposed to roll the bacon soup can so he just yeets it out of the hallway and it almost hits a crew member
Alice can’t break the glass and needs help getting out
The same thing happens with the Piper behind the poster
Half the time Bendy forgets he needs to make a portal and smacks into the wall
He also doesn’t chase Henry when he should sometimes
The ink dial machine things break a lot
Henry and Alice actually get along well so most scenes between them are hilarious
The Projectionist forgets to warn everyone how loud his shriek is so Henry and the crew member manning the boom mic get their ears killed
The elevator crash is filmed with a green screen so it’s just Alice yelling, Boris cowering, and Henry running around
The pulley actually breaks when Henry is halfway across the chasm
Alice’s mic breaks in the middle of her monologue
“And he referred to me, the great Bertie Piedmont, as Bertie! Wait-”
It’s pretty common for the carnival games to break so someone has to get Lacie and Bertie so that Wally and Thomas can help fix them
The Bendy animatronic disappears one day during filming. It’s back in its place the next day. Nobody knows who moved it
The Butcher Gang messing around with props while the camera’s rolling
The Projectionist dodges one of Bendy’s punches and falls down the stairs
Norman’s head doesn’t actually come off (they use practical effects), but it looks so real that it freaks out most of the crew the first time they film the scene
The sound system breaks during Bertie's speech
Normal Boris pops out instead of Brute Boris
Since Boris was previously thought to be Wally, he keeps saying “I’m gonna kill ya!” like he does in the Bendy Royale trailer while they’re filming the Brute Boris fight
Alice trips while running out to kill Henry
Allison keeps missing Alice’s chest with her sword
In one take she hits her head
Alice doesn’t really get stabbed; they use a trick like the one in Beetlejuice when Lydia stabs BJ
“I don’t know my name. So they call me Allison-Alice, dangit.”
The boat breaks a lot
Sammy hits the boards so hard that they fly off
Tom misses when he goes to hit Sammy; he probably hits Henry at some point
The board doesn’t break so Henry just walks across
Everyone gets lost in Administration. Even the set designers. Nobody is safe from it
Bendy trips while walking past the glass
Bendy doesn’t transform into Beast Bendy
When he does, he tries and fails to smack Henry through the wall
The reel doesn’t play
Joey’s little pocket dimension doesn’t work and there’s just a wall when Henry opens the door