Why do these boulders keep multiplying and disappearing?

Question

In this video, a fish is playing Pokemon and screwed up the strength puzzle, at timestamp 0:43. Without leaving the cave to refresh it, in a few minutes the boulders reset (at like 1:19). Is this a glitch, or a programming quirk in case the player is stuck?

Edit: I watched more of the video and at 1:55 the boulders reset??? so uh I'm going to change this question to why and how this happened

I WATCHED THE END OF THE VIDEO AND THEY KEEP MULTIPLYING WHY

Comments

Are you from Japan?

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No, but i have japanese family and I can speak some. why?

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https://twitter.com/eclipse_tt/status/1314650152381100039
This might help

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oh my gosh its called the Fish Glitch

Answer 1

In the Seafloor Cavern, in the second-to-last room, there is a Strength boulder puzzle that the player can accidentally make unsolvable. The game will reset the position of some boulders when the player walks away from them to make puzzle solveable again; however, one of the boulders doesn't get reset properly, and its tile will contain two boulders at once.
This glitch was first discovered by the Mutemikaru Channel.

There you go, the game wants to make the puzzle able to be solved, but doesn't reset properly resulting in this glitch.

Source: https://m.bulbapedia.bulbagarden.net/wiki/List_of_glitches_in_Generation_III