This is a bit of a tricky thing but it leads to the following PHP error and a blank page on the contact form: “PHP Warning: json_encode(): Invalid UTF-8 sequence in argument”
When using the “Add Contact” button while editing a meeting and saving the new contact, the DEFAULT VALUES for the contact fields that contain german Umlauts get XML encoded instead of saved as an UTF-8 character. The form fields themselves get saved correctly.
In the database f.e. the string “Mäxchen” gets saved as “Mäxchen”.
When opening the contact from the contact list, a blank page appears together with the above error in the apache error log.