Redmine

Sorry, the redmine log (production.log file).

We have since discovered that the user can create and update tickets himself, but can't assign them to anyone. He can assign the ticket to himself, but after that he can't update it anymore. If he re-assigns it to noone he can update it again. We've only tested this with new tickets that have no previous assignment history.

Thank you so much for looking into this!

How about Webserver log?
Please describe more details about "Internal Error".

The error we get in the browser looks like this:

Internal error

An error occurred on the page you were trying to access.
If you continue to experience problems please contact your Redmine administrator for assistance.

If you are the Redmine administrator, check your log files for details about the error.

Good thinking about the apache error log. Here are the relevant lines. I replaced my private info with "..."

App 6308 stderr: Started PATCH "/issues/905" for ... at 2016-08-31 19:18:01 +0000
App 6308 stderr: Processing by IssuesController#update as HTML
App 6308 stderr:   Parameters: {...}
App 6308 stderr:   Current user: ...
App 6308 stderr:   Rendered mailer/_issue.text.erb (15.7ms)
App 6308 stderr:   Rendered mailer/issue_edit.text.erb within layouts/mailer (16.2ms)
App 6308 stderr:   Rendered mailer/_issue.html.erb (1.9ms)
App 6308 stderr:   Rendered mailer/issue_edit.html.erb within layouts/mailer (3.4ms)
App 6308 stderr: Completed 500 Internal Server Error in 365ms (ActiveRecord: 140.0ms)
App 6308 stderr:
App 6308 stderr: OpenSSL::SSL::SSLError (hostname "..." does not match the server certificate):
App 6308 stderr:   app/models/mailer.rb:458:in `deliver_mail'
App 6308 stderr:   config/initializers/10-patches.rb:154:in `deliver'
App 6308 stderr:   app/models/mailer.rb:98:in `block (2 levels) in deliver_issue_edit'
App 6308 stderr:   app/models/issue.rb:952:in `each_notification'
App 6308 stderr:   app/models/mailer.rb:97:in `block in deliver_issue_edit'
App 6308 stderr:   app/models/journal.rb:90:in `block in each_notification'
App 6308 stderr:   app/models/journal.rb:88:in `each'
App 6308 stderr:   app/models/journal.rb:88:in `each_notification'
App 6308 stderr:   app/models/mailer.rb:96:in `deliver_issue_edit'
App 6308 stderr:   app/models/journal.rb:302:in `send_notification'
App 6308 stderr:   app/models/journal.rb:67:in `save'
App 6308 stderr:   app/models/issue.rb:1672:in `create_journal'
App 6308 stderr:   app/models/issue.rb:182:in `create_or_update'
App 6308 stderr:   app/controllers/issues_controller.rb:487:in `block in save_issue_with_child_records'
App 6308 stderr:   app/controllers/issues_controller.rb:475:in `save_issue_with_child_records'
App 6308 stderr:   app/controllers/issues_controller.rb:180:in `update'
App 6308 stderr:   lib/redmine/sudo_mode.rb:63:in `sudo_mode'

Looks like this is the issue here:

App 6308 stderr: OpenSSL::SSL::SSLError (hostname "..." does not match the server certificate):

I am using a different mail server than the server that redmine is running on. That should be ok, right? It's been ok so far anyway and nothing has changed on the redmine server. It just suddenly stopped working.

So I contacted my mail provider and it turns out they moved servers without telling us. I updated the redmine configuration.yml accordingly and it's working again. Problem solved. Thank you so much for steering me in the right direction!