Looking at a furniture item with a changeable state (tested on a barrel but presumably works on other things like chests, crates, etc) when another player changes the item's state causes the look window to be uncloseable. 

For example, if a player looks at a barrel while another player takes a cup of water from the barrel, the player can no longer close the look window. ESC menu doesn't work in this state so the only fix is to close the entire game window.

This also seems to happen when a critter looks at a preparation table while someone else uses it!