Double token check in devise - ruby-on-rails

Question

Devise is acting weird for the first time each day when a User tries to create a new User in our project. This is the server log from the exact moment the user clicks on the confirm link:
Started GET "/users/confirmation?confirmation_token=3F367iMzUm5y3ohbkykM" for 199.116.169.254 at 2014-07-22 15:34:29 +0000
Processing by Devise::ConfirmationsController#show as */*
Parameters: {"confirmation_token"=>"3F367iMzUm5y3ohbkykM"}
Redirected to http://qa.nearshoreconnect.com/users/sign_in
Completed 302 Found in 228ms (ActiveRecord: 2.2ms)
Started GET "/users/sign_in" for 199.116.169.254 at 2014-07-22 15:34:29 +0000
Processing by Devise::SessionsController#new as */*
Rendered layouts/_errors.html.erb (0.1ms)
Rendered devise/sessions/new.html.erb within layouts/application (6.1ms)
Rendered layouts/_shim.html.erb (0.4ms)
Rendered layouts/_search_box.html.erb (1.2ms)
Rendered layouts/_header_internet.html.erb (9.6ms)
Rendered layouts/_footer_internet.html.erb (1.4ms)
Completed 200 OK in 29ms (Views: 27.5ms | ActiveRecord: 0.0ms | Solr: 0.0ms)
Started GET "/users/confirmation?confirmation_token=3F367iMzUm5y3ohbkykM" for 201.234.55.21 at 2014-07-22 15:34:30 +0000
Processing by Devise::ConfirmationsController#show as HTML
Parameters: {"confirmation_token"=>"3F367iMzUm5y3ohbkykM"}
Rendered layouts/_errors.html.erb (0.7ms)
Rendered devise/confirmations/new.html.erb within layouts/application (3.9ms)
Rendered layouts/_shim.html.erb (0.4ms)
Rendered layouts/_search_box.html.erb (1.0ms)
Rendered layouts/_header_internet.html.erb (2.6ms)
Rendered layouts/_footer_internet.html.erb (1.3ms)
Completed 200 OK in 18ms (Views: 14.1ms | ActiveRecord: 0.3ms | Solr: 0.0ms)
Started GET "/assets/font.css" for 201.234.55.21 at 2014-07-22 15:34:30 +0000
Served asset /font.css - 304 Not Modified (0ms)
The validation token is checked twice. I'm overriding the confirm function in my User model. Is that the problem? The code:
def confirm!
super
send_welcome_mail
end