German umlauts in the create dialog

Hey,
i have a problem with the german umlauts (ö, ä, ü) in the create page dialog and in the space content section.
If i create a page from my blueprints with umlauts in the page content it’s not a problem with umlauts. Only in the create page dialog and in the space content section it’s wrong.

Screenshot:
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The files in my plugin encode with UTF-8.
Can anybody help me?