All characters jump off the platform in multiplayer

Good afternoon, help please, we made a platform on which you can jump and fall, but when I press the “S” key, all the characters fall, but you need to make sure that the character who pressed “S” falls and the others do not fall, if a character jumps onto the platform and another character presses “S”, then a character who for some reason is on the platform will fall
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as I understand it, the “s” key just works on all characters, but how to differentiate