Repeated use of /fill and /clone to build structures sometimes results in a circumstance where the updated blocks do not immediately appear after issuing the command. Disconnecting from the server and reconnecting then results in very strange visual artefacts that flicker rapidly through various configurations from frame to frame. These artefacts seem to be related to some sort of corruption in the client state; repeatedly signing out and back in does not clear the artefacts, but a full restart of the client does, without requiring any action on the server.