Sign Texts with Added "s and /s every time i rejoin a world

so in a world i made i had some signs. every time i would save and quit to title and then rejoin later some "s or /s were added to the sign and eventually it just filled the entire sign after like 5 times.
with the screen shots they go in order and in between each one i save and quit and then rejoined the world.
Note this is a single player world