Redmine

When viewing specific issues I'm getting an Internal Error message. Checking the production.log file it gives me the following error:

Started GET "/issues/23" for 76.173.208.56 at 2014-01-12 20:44:55 -0500
Processing by IssuesController#show as HTML
Parameters: {"id"=>"23"}
Current user: Ruben (id=3)
Rendered issues/_action_menu.html.erb (5.3ms)
Rendered issues/show.html.erb within layouts/base (78.7ms)
Completed 500 Internal Server Error in 153ms

ActionView::Template::Error (incompatible character encodings: UTF-8 and ASCII-8BIT):
78:
79: <p><strong><%=l(:field_description)%></strong></p>
80: <div class="wiki">
81: <%= textilizable @issue, :description, :attachments => @issue.attachments >
82: </div>
83: </div>
84: < end %>
app/views/issues/show.html.erb:81:in `_app_views_issues_show_html_erb__2242756398372498208_70142826780600'
app/controllers/issues_controller.rb:124:in `block (2 levels) in show'
app/controllers/issues_controller.rb:121:in `show'

This only happens with some specific issues, probably ones containing special characters (guessing).

The MySql database collation is set to UTF-8. I read some similar bug reports here, some of which stating that switching to the mysql2 adapter would solve it. I was indeed using the old mysql connector and switched to mysql2 (as you can see in the report below). After this change I cleared the cache and sessions, but the problem persists.

This is my environment info:

Environment:
Redmine version 2.3.3.devel
Ruby version 2.0.0-p353 (2013-11-22) [x86_64-linux]
Rails version 3.2.13
Environment production
Database adapter Mysql2
SCM:
Git 1.7.1
Filesystem
Redmine plugins:
no plugin installed