Hi Christophe,
Greetings from Syncfusion,
We have checked the reported scenario at our end. We are able to reproduce the report the issue at our end. We confirm this as a bug and logged a defect report. You can keep track of the bug from the feedback portal below.
https://www.syncfusion.com/feedback/4424/
The fix will be available in our volume 4 service pack 1 release which is scheduled to be rolled out at February 4, 2019.
If you have any more specification/precise replication procedure or a scenario to be tested, you can add it as a comment in the portal.
Regards,
Baby.