Restoring collection creates new model instances

[Grid405]

Hi River Lynn,

thank you for this awesome plugin, after all these years i'm still using it a lot.
I recently ran into an issue with collections that contain models that are also contained in other collections.
Using restore on a collection causes the collection to discard the original model instances and create new ones, after which changing a model in that collection won't affect the same model in another collection anymore, because they are no longer the same instance.
If it doesn't create other problems down the line, it seems beneficial if the original model instances would be kept when restoring a collection.