When you are the guest of a server sometimes randomly, while placing down items, (i.e. conveyor belts or foundation) you will hear what sounds like that item being placed down many time in rapid succession. Then the item will appear as if it was never placed. You will still collide with it as if it were there but in a glitchy sort of manner. The host of the server can see the item just fine. If the guest of the server disconnects and reconnects, the item will appear. This seems to happen after the server has been up for at least 2 hours.