Remove any associated event listeners from the object.
Call removeSelf() on the display object.
Set the display object’s variable to nil.
In the latest iteration of cleangroup.lua (1.1), as a “backup defense”, I added a check for any touch listeners to display objects before they are removed. You should always follow the best practices above, but the new update should help &just in case you forget to remove any touch listeners from an object before calling removeSelf().