Rails I18n locale changing does not work as expected

I am currently dealing with I18n and am facing a problem.

The locale.rb:

I18n.load_path += Dir[Rails.root.join('config', 'locale', '*.{rb,yml}')]
I18n.available_locales = [:de, :en, :es]
I18n.default_locale = :en

For changing the locale i have a little partial which works fine:

<% I18n.available_locales.each do |lang| %>
	<a href="<%= url_for(:locale => lang)%>" class=" text-gray-300 e">
		<%= lang %>
<% end %>

In my routes i have the following:

root to: redirect("/#{I18n.default_locale}"), as: :redirected_root
	scope "(:locale)", locale: /#{I18n.available_locales.join("|")}/ do

		root "home#index"
... more code

Here is a Screenshot:

The redirect to the current locale also works fine. When i load my page, the locale will set to :de When i click on another language, the locale will change successfully.

Now to the problems: When i click on checklists the locale will removed and the URL changes to http://localhost:3000/checklists.

When clicking another locale for more than one time the URL change to http://localhost:3000/de/es/checklisten, it has two locales.

Why is that so?

I couldn’t find a solution via google.

Does anyone has an idea for fixing that issue?