I have 2 different calls to the same Devise method: destroy_user_session.
The working one is done with a very basic approach and lead to the following HTML code:
<a rel="nofollow" data-method="delete" href="/users/sign_out">Logout</a>
Them I made a more fancy one, with better UI, but still the same Rails App (so no change, only the resulting HTML is different):
<a class="tip" data-confirm="You are going to be disconnected" data-title="Logoff" rel="nofollow" data-method="delete" href="/users/sign_out" data-original-title="" title=""><i class="fa fa-power-off"></i></a>
While both are using the same method: delete to destroy current user session the second one returns No route matches [GET] "/users/sign_out".
Adding a GET route for /users/sing_out can be an option but not clean as it has to be a DELETE call.
Issue was created by "rails ujs javascript" not loading properly on the faulty page.