The appearance changes of the instances on the layers now follow the edited objects through the same pass as the instances in other symbols, graph designs, pattern tiles and brushes. That pass also reaches instances used as opacity-mask art, which keep their changes on the same objects when an edit reorders them and drop the change to an object the edit deletes.
Editing a dynamic symbol moved each placed instance's appearance changes with the objects they
name, but an instance stored in the art of another symbol kept its changes at the old paths, so
placing that symbol showed a change on the wrong object. Those instances, opacity masks included,
now follow the edit too and keep only the changes to objects the art still has.
symbol.edit checks the new placement before it ends the symbol being edited, so a call with an out-of-range x or y fails and leaves the current edit open. While a symbol is edited, object.isolate refuses art outside the editing layer, and object.exitIsolation goes back to the editing layer only from a group inside it; from any other isolation it leaves symbol editing mode.