Inconsistent and brittle trait inheritance behavior

Given this this class and this factory definition:

DataClass = Struct.new(:x, :y, :z)

FactoryGirl.define do
  factory :parent_factory, class: DataClass do
    x 1

    trait :y do
      y 1
    end

    trait :z do
      y
      z 1
    end
  end

  factory :child_factory, class: DataClass, parent: :parent_factory do
    x 2

    trait :y do
      y 2
    end
  end
end

You observe this behaviour:

require 'factory_girl'
FactoryGirl::VERSION
# => '4.7.0'

FactoryGirl.find_definitions
FactoryGirl.build(:parent_factory, :z)
# => <struct DataClass x=1, y=1, z=1>
FactoryGirl.build(:child_factory, :z)
# => <struct DataClass x=2, y=1, z=1>

FactoryGirl.reload
FactoryGirl.build(:child_factory, :z)
# => <struct DataClass x=2, y=2, z=1>
FactoryGirl.build(:parent_factory, :z)
# => <struct DataClass x=1, y=2, z=1>

Reproduce the behavior through FactoryGirl.find_definitions, FactoryGirl.build, and FactoryGirl.reload using the factory and trait definitions in the report. Trace how parent and child traits are resolved before and after reload. Done means trait inheritance produces consistent results regardless of build order or whether FactoryGirl.reload was called.