diff --git a/crystalball.gemspec b/crystalball.gemspec
index 5069d505..5c09e58c 100644
--- a/crystalball.gemspec
+++ b/crystalball.gemspec
@@ -41,7 +41,8 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency 'parser'
   spec.add_development_dependency 'pry'
   spec.add_development_dependency 'pry-byebug'
-  spec.add_development_dependency "rake", "~> 10.0"
+  spec.add_development_dependency 'psych', '~> 4.0.0'
+  spec.add_development_dependency "rake"
   spec.add_development_dependency "rspec", "~> 3.0"
   spec.add_development_dependency 'rubocop', ">= 0.56"
   spec.add_development_dependency 'rubocop-rspec'
diff --git a/lib/crystalball/extensions/git/lib.rb b/lib/crystalball/extensions/git/lib.rb
index 4c45ee9d..6092c10d 100644
--- a/lib/crystalball/extensions/git/lib.rb
+++ b/lib/crystalball/extensions/git/lib.rb
@@ -12,7 +12,7 @@ def merge_base(*args)
 
       arg_opts = opts.map { |k, v| "--#{k}" if v }.compact + args
 
-      command('merge-base', arg_opts)
+      command('merge-base', arg_opts.each { |opt| return opt })
     end
   end
 end
diff --git a/lib/crystalball/map_generator/factory_bot_strategy/factory_runner_patch.rb b/lib/crystalball/map_generator/factory_bot_strategy/factory_runner_patch.rb
index cc7c18ed..d040f6d2 100644
--- a/lib/crystalball/map_generator/factory_bot_strategy/factory_runner_patch.rb
+++ b/lib/crystalball/map_generator/factory_bot_strategy/factory_runner_patch.rb
@@ -15,7 +15,7 @@ def apply!
         # Overrides `FactoryBot::FactoryRunner#run`. Pushes factory name to
         # `FactoryBotStrategy.used_factories` and calls original `run`
         def run(*)
-          factory = FactoryBotStrategy.factory_bot_constant.factory_by_name(@name)
+          factory = FactoryBotStrategy.factory_bot_constant::Internal.factory_by_name(@name)
           FactoryBotStrategy.used_factories << factory.name.to_s
           super
         end
diff --git a/lib/crystalball/map_storage/yaml_storage.rb b/lib/crystalball/map_storage/yaml_storage.rb
index 473cc09d..df54995d 100644
--- a/lib/crystalball/map_storage/yaml_storage.rb
+++ b/lib/crystalball/map_storage/yaml_storage.rb
@@ -33,7 +33,7 @@ def read_files(path)
 
           paths.map do |file|
             metadata, *example_groups = file.read.split("---\n").reject(&:empty?).map do |yaml|
-              YAML.safe_load(yaml, [Symbol])
+              YAML.safe_load(yaml, permitted_classes: [Symbol])
             end
             example_groups = example_groups.inject(&:merge!)
 
@@ -42,7 +42,8 @@ def read_files(path)
         end
 
         def guard_metadata_consistency(metadata)
-          uniq = metadata.uniq
+          # check for consistency except for timestamp - to enable parallel map generation
+          uniq = metadata.uniq{ |m| m.keys.concat(m.values_at(:type, :commit, :version)) }
           raise "Can't load execution maps with different metadata. Metadata: #{uniq}" if uniq.size > 1
         end
       end
diff --git a/lib/crystalball/rails/map_generator/i18n_strategy/simple_patch.rb b/lib/crystalball/rails/map_generator/i18n_strategy/simple_patch.rb
index 7b77bbbe..21721705 100644
--- a/lib/crystalball/rails/map_generator/i18n_strategy/simple_patch.rb
+++ b/lib/crystalball/rails/map_generator/i18n_strategy/simple_patch.rb
@@ -37,15 +37,16 @@ def revert!
           # Will replace original `I18n::Backend::Simple#load_file`.
           # Stores filename in current thread
           def cb_patched_load_file(filename, *args)
-            Thread.current[:cb_locale_file_name] = filename
+            set_cb_locale_file_name(filename)
             cb_original_load_file(filename, *args)
           end
 
           # Will replace original `I18n::Backend::Simple#store_translations`.
           # Adds filename for each value
           def cb_patched_store_translations(locale, data, *args)
-            cb_add_filename_to_values(data, Thread.current[:cb_locale_file_name])
-            cb_original_store_translations(locale, data, *args)
+            data_unfreeze = data.dup
+            cb_add_filename_to_values(data_unfreeze, get_cb_locale_file_name)
+            cb_original_store_translations(locale, data_unfreeze, *args)
           end
 
           # Will replace original `I18n::Backend::Simple#lookup`.
@@ -57,6 +58,14 @@ def cb_patched_lookup(*args)
 
           private
 
+          def set_cb_locale_file_name(filename)
+            Thread.current[:cb_locale_file_name] = filename
+          end
+
+          def get_cb_locale_file_name
+            Thread.current[:cb_locale_file_name]
+          end
+
           def cb_add_filename_to_values(data, filename)
             data.each do |key, value|
               case value
diff --git a/lib/crystalball/rspec/runner.rb b/lib/crystalball/rspec/runner.rb
index e124f735..920fb74a 100644
--- a/lib/crystalball/rspec/runner.rb
+++ b/lib/crystalball/rspec/runner.rb
@@ -41,7 +41,7 @@ def config
           @config ||= begin
             config_src = if config_file
                            require 'yaml'
-                           YAML.safe_load(config_file.read)
+                           YAML.safe_load(config_file.read, permitted_classes: [Symbol])
                          else
                            {}
                          end
diff --git a/spec/map_generator/factory_bot_strategy/factory_runner_patch_spec.rb b/spec/map_generator/factory_bot_strategy/factory_runner_patch_spec.rb
index 57f5e722..da0ca105 100644
--- a/spec/map_generator/factory_bot_strategy/factory_runner_patch_spec.rb
+++ b/spec/map_generator/factory_bot_strategy/factory_runner_patch_spec.rb
@@ -42,8 +42,9 @@ def run(*); end
     let(:used_factories) { [] }
 
     before do
+      class_double('FactoryBotConstant::Internal', factory_by_name: nil).as_stubbed_const
       allow(Crystalball::MapGenerator::FactoryBotStrategy).to receive(:used_factories).and_return(used_factories)
-      allow(FactoryBotConstant).to receive(:factory_by_name).with(:bad_dummy) { double(name: :dummy) }
+      allow(FactoryBotConstant::Internal).to receive(:factory_by_name).with(:bad_dummy) { double(name: :dummy) }
       instance.instance_variable_set(:@name, :bad_dummy)
     end
 
diff --git a/spec/map_generator_spec.rb b/spec/map_generator_spec.rb
index d3da2127..12db104b 100644
--- a/spec/map_generator_spec.rb
+++ b/spec/map_generator_spec.rb
@@ -87,7 +87,7 @@ def s.call(example_group_map, _example)
       end
 
       it 'dump new map metadata to storage' do
-        expect(storage).to receive(:dump).with(type: map_class.to_s, commit: 'abc', timestamp: 1234, version: 1.0)
+        expect(storage).to receive(:dump).with({ type: map_class.to_s, commit: 'abc', timestamp: 1234, version: 1.0 })
         subject.start!
       end
 
@@ -181,7 +181,7 @@ def example_map(uid)
           allow(configuration.strategies).to receive(:run).with(kind_of(Crystalball::ExampleGroupMap), any_args)
                                                           .and_return(example_map('1'), example_map('2'), example_map('3'))
 
-          expect(storage).to receive(:dump).with('1' => [], '2' => []).once
+          expect(storage).to receive(:dump).with({ '1' => [], '2' => [] }).once
           expect_any_instance_of(map_class).to receive(:clear!).once.and_call_original
           subject.refresh_for_case(rspec_example('1'))
           subject.refresh_for_case(rspec_example('2'))
diff --git a/spec/rails/map_generator/i18n_strategy/simple_patch_spec.rb b/spec/rails/map_generator/i18n_strategy/simple_patch_spec.rb
index e9b641dc..4d812a40 100644
--- a/spec/rails/map_generator/i18n_strategy/simple_patch_spec.rb
+++ b/spec/rails/map_generator/i18n_strategy/simple_patch_spec.rb
@@ -67,11 +67,12 @@ def lookup; end
     let(:locale) { :en }
     let(:data) { {user: {name: 'John'}} }
     let(:filename) { 'locale/foo.yml' }
+    let(:thread) { class_double(Thread) }
 
-    before { allow(Thread.current).to receive(:[]).with(:cb_locale_file_name) { filename } }
+    before { allow_any_instance_of(described_class).to receive(:get_cb_locale_file_name).and_return(filename) }
 
     it do
-      expect(instance).to receive(:cb_original_store_translations).with(locale, user: {name: {cb_filename: filename, cb_value: 'John'}})
+      expect(instance).to receive(:cb_original_store_translations).with(locale, { user: {name: {cb_filename: filename, cb_value: 'John'}} })
       subject
     end
 
diff --git a/spec/rails/tables_map_generator_spec.rb b/spec/rails/tables_map_generator_spec.rb
index 77667f46..195d5cd2 100644
--- a/spec/rails/tables_map_generator_spec.rb
+++ b/spec/rails/tables_map_generator_spec.rb
@@ -74,7 +74,7 @@
       end
 
       it 'dump new map metadata to storage' do
-        expect(storage).to receive(:dump).with(type: map_class.to_s, commit: 'abc', version: 1.0)
+        expect(storage).to receive(:dump).with({ type: map_class.to_s, commit: 'abc', version: 1.0 })
         subject.start!
       end
     end
@@ -101,7 +101,7 @@
         end
 
         specify do
-          expect(storage).to receive(:dump).with('Dummy' => ['file1'])
+          expect(storage).to receive(:dump).with({ 'Dummy' => ['file1'] })
           subject.finalize!
         end
       end
diff --git a/spec/rspec/runner_spec.rb b/spec/rspec/runner_spec.rb
index d5c1c17a..d47670f4 100644
--- a/spec/rspec/runner_spec.rb
+++ b/spec/rspec/runner_spec.rb
@@ -24,7 +24,7 @@
     end
 
     context 'with CRYSTALBALL_CONFIG env variable set' do
-      let(:expected_config) { YAML.safe_load(Pathname('spec/fixtures/crystalball.yml').read) }
+      let(:expected_config) { YAML.safe_load(Pathname('spec/fixtures/crystalball.yml').read, permitted_classes: [Symbol]) }
 
       around do |example|
         ENV['CRYSTALBALL_CONFIG'] = 'spec/fixtures/crystalball.yml'