It was on the 2nd stage all the way in the room to the far left where you have to I assume double jump up. I got stuck on the single blocks on the right side of that room
I wasn't sure if I could make the jump from the left to the right so I started climbing up to the right and got stuck up in there. I just beat the game though! Really clever mix of the level all being the same level but only revealed once you get the camera! Fantastic job!