While breaking blocks or changing a block's state, the game 'lags' and does not visually recognize that the state has changed. In both the screenshots below the door is open, and the game shows it as being open, but it is visually closed. It will fix upon updating the block, such as closing and opening the door again. This same issue is present with chests in LAN servers, though is less prevalent. For example, a friend playing on the LAN server will open a chest, and the chest lid will open, but the chest will also remain closed. It makes the chest look like there are two chests inside each other. The only fix I found is restarting the server.