Command Block stops

I was making a water dispenser with a command block, then the command block suddenly stopped. I used the command:  particle minecraft:dripping_water ~ ~3 ~ , with the command block on repeat, unconditional and always active. if i looked in the command block GUI i can type, but i cannot select the 3 bottom buttons. [edit] i did a restart and it seemed to work but after a while it happened again.