Piston+slimeblock duplication glitch

I made a hopper + compator clock, attached to 4 sticky pistons with slime blocks on top. when i ran it, three of the four pistons where pushed up, like normal, but if i flew some distance, but i could still see it. it would some how create for of the blocks. this would continue even if i got close to it again. it would also duplicate any block connected to set slime blocks.