Since the latest update placed pipes will randomly despawn. Sometimes when the pipe is placed another despawns, sometimes it takes 5 minutes sometimes an hour.
About the empty blocks, Those are block places, where you could walk through without any issue but the game won't let you place anything. I've noticed with an aqueduct that the water does not seem to care about the empty block and keeps flowing at the same level.
This is all on a vanilla server with no mods.
Any help? or just a bug that needs fixing?