Currently, the following code raises Mongoid::Errors::DocumentNotFound

class Person
  include Mongoid::Document

  embeds_many :phones

  accepts_nested_attributes_for :phones
end

class Phone
  include Mongoid::Document

  embedded_in :person
end

person = Person.create!
person.update_attributes!(phones_attributes: [{ id: 'a' * 24, _destroy: true }])
#=> raises Mongoid::Errors::DocumentNotFound

It looks like this happens because the code first tries to "find" the embedded object (which raises error) before attempting to delete it.

In this case, it would be much better to just ignore the non-existent embedded object, because it was probably already deleted. This seems to happen a lot in parts of the app where many users might be trying to modify the same object.