Redmine

When opening the profile page for a specific user internal server occurs:

I, [2016-03-07T09:33:19.696602 #1600]  INFO -- : Started GET "/users/5/" for X.X.X.X at 2016-03-07 09:33:19 +0100
I, [2016-03-07T09:33:19.697375 #1600]  INFO -- : Processing by UsersController#show as HTML
I, [2016-03-07T09:33:19.697416 #1600]  INFO -- :   Parameters: {"id"=>"5"}
I, [2016-03-07T09:33:19.699316 #1600]  INFO -- :   Current user: the.user (id=5)
I, [2016-03-07T09:33:19.788476 #1600]  INFO -- : Completed 500 Internal Server Error in 91ms (ActiveRecord: 26.6ms)
F, [2016-03-07T09:33:19.789240 #1600] FATAL -- : 
ArgumentError (comparison of TimeEntry with JournalMessage failed):
  lib/redmine/activity/fetcher.rb:95:in `sort!'
  lib/redmine/activity/fetcher.rb:95:in `events'
  app/controllers/users_controller.rb:75:in `block (2 levels) in show'
  app/controllers/users_controller.rb:73:in `show'
  lib/redmine/sudo_mode.rb:63:in `sudo_mode'

This happens only for one user (id 5). It does not matter who accesses the site. Any ideas?

Environment:
  Redmine version                3.1.1.stable
  Ruby version                   2.1.5-p273 (2014-11-13) [x86_64-linux-gnu]
  Rails version                  4.2.4
  Environment                    production
  Database adapter               Mysql2
SCM:
  Subversion                     1.8.10
  Git                            2.1.4
  Filesystem                     
Redmine plugins:
  redmine_contacts               4.0.3
  redmine_contacts_helpdesk      3.0.1