If you have code that adds commands to Chimera using the addCommand() function, there is a new keyword to that function so that animation scripts can work better. The keyword is 'changesDisplay' and is a boolean that defaults to True. If your command typically changes the display in the main graphics window somehow the keyword should be True, otherwise False. It's needed so that as a script is executed, Chimera knows after each line whether a new frame is necessary or not. For instance, for the 'alias' command the value is False since after executing that command in a script you would not want to record a new frame in an animation.
--Eric