TYPO3 Core

My Backend is in German and all translations are there. However, when I view the Filelist module and hit the "Upload file" button, the texts in the upcoming container are untranslated. See screenshot.

The according texts are taken from typo3/sysext/backend/Resources/Public/JavaScript/DragUploader.js.
E.g. the title uses the language label "file_upload.dropzonehint.title". For this label I do have a German translation in typo3conf/l10n/de/lang/de.locallang_core.xlf. However, the labels in this container only show up in English.

It seems like translation of these labels is broken...