Cannot use command blocks

Every time i place down a command block i type a command in it then exit and go back in the command is gone. Furthermore, i cannot alter the type i cannot change it from repeat to impulse it changes but as soon as i click it again it goes right back to a repeat command block. This is happening on my realm in a single player world this doesn't occur.

Just checked when i attempt to pick block the command block as the impulse it pick blocks it as a repeating command block not an impulse. I am afraid to touch any command block on my realm because of this. Fix this ASAP