There is a problem with cloning model with localized fields:

class ModelB < SubclassWithMongoid
field :title, localize: true
end

m = Model.new(title: "Hello")
m.title => "Hello"

mc = m.clone
mc.title => "

{ "en" => "hello" }"

I think is because of:
https://github.com/mongoid/mongoid/blob/master/lib/mongoid/copyable.rb#L21

First document is transformed to hash like:
{"_id"=>"510ba9e6a46d822ace000002", title => { "en" => "hello" }

, _type => "ModelB" }

It should be this:
{"_id"=>"510ba9e6a46d822ace000002", title_translations =>

{ "en" => "hello" }

, _type => "ModelB" }