This is because you are not closing the acad lt. In the script file (.scr) you will need to send all of the commands that are required for that drawing. Calling acad lt from the command line (which is the only way I know of to do this) means that it is all by itself and you have no control. So in the script file close acad after the commands are through. Then start another script. To repeat you cannot reuse an existing instance of acad lt via a script file or anything else other than human intervention.