Hi Wolfgang Schneider,
Thanks for contacting syncfusion support.
We have checked your query. The reported issue is a known issue that was planned to be worked in the upcoming days. The fix for this issue will be available in the upcoming 2017 volume 4 service pack 1 release scheduled for roll out on the last week of December.(Tentative) We appreciate your patience until then.
Regards,
Shivagurunathan. K