Sign texts are disappearing as I place them down

After trying to set a command block down to change the difficulty consistently, I used the /gamerule comandBlockOutput so I dont get spammed in chat and after doing so, every time I place a sign down with texts, the sign words show up for a second and go blank. Even using the command /data get block x y z tells me that the sign has no text on it. This only happened after I tried to use a command block. It even happened to my friend but it is fine for him sometimes.