I was setting up command blocks to clone other command blocks in a straight pillar, this would repeat until it goes to world height (in a old style world) When it reached the point where it could not clone them anymore because of world height it would begin cause periodic lag spikes that would last for any given amount of time. If you tried to exit to main menu it would cause the game to freeze and you can't do anything without alt F4ing the game, if you try to load back into the world everything gets reset aside from your inventory (I only did this on newly created worlds that had not been closed before so it may just undo everything since the last time you close the world) The commands used were as follows, (Chain Command Block) Clone ~ ~-1 ~ ~1 ~ ~ ~ ~. Underneath that block was a normal command block that was not active when the bug occurred, fill x ~-1 z x ~-1 z water 0 replace air. And on top of the chain command block was another chain command block with the command. Fill ~ ~-2 ~ ~ ~-2 ~ air. The first time this happened the first two commands where the same except the normal command block was always active and activated every 660 ticks, the third command block was not involved, the second time this happened the normal command block was set to not activate but was still there with the other two being constantly active. To reiterate the issues only began when the command blocks reached world height in an old style world. After the command blocks are broken the issue persists until you close game.

Thank You