I put up a LAN World (No players have to join) and close it. When I start the world again some of my full clocks (Clocks where 2 fill commands set air and redstone blocks to run commands every tick) stop working. The redstone block no longer gets replaced by air. Strangely all clocks which stopped working where in a Extreme Hills, Plains biome will all which keept working where in a Savanna biome. But i don't now if this has anything to say.

This only happens when i open the world for lan.