Another wrong/bad german translation was introduced with 5.3.9.x
When editing a field in a field-set, field type dropdown-select:
New: “- Wähle -” (gives the impression that no type is selected)
Old: “Auswahlmenü” (correct)
Edit: Both issues are solved in the meantime, had to trigger a manual WPML re-scan of ACF Plugin, now correct strings show up. Had an old version of ACF installed long ago, seems WPML remembered these old strings…