So, I was in a standard run. The bell tower glitch, when the bell rings when you enter the room, starts happening. This isn't the first time it happened to me so I just started from the opposite side of the bell and got the Anti-cube as usual. But then, once I entered the Puzzle anti-cube in the next room, it just skipped the puzzle, simply. I don't know if this is a known issue and if this is completely random or if you could set it up. Here's the video :

You didn't reset the game after a run where you completed that anticube puzzle, so it carried over information from the previous run and auto completed. It's a known glitch and banned under save manipulation.

Ooooh I see, I have never heard of that until now ! Thanks a bunch !