When using umlaute (presumably special characters in general) like ä in the page title, the Rich Text editor has problems with the encoding. It seems like after saving the page, the problem starts to occur.

Example:

1. Create a new page
2. setting page title to: Hallo ÖÄÜ
3. Adding link to the new page in page 2, save, link is ok.
4. Editing page 2, press save and the link is shown correct but the plus sign appears for creating new page.
5. when editing page 2 again the link looks like this: Hallo ÖÄÜ (in the wiki markup: Hallo ÖÄÜ)