Hi Julien,
Greetings from Syncfusion support.
Query:” Expand arrow now redirects to root ?”
Based on your query and provided screenshots, we suggest you
to update to the latest version in both style and script to avoid
redirecting.
Screenshot: 
Sample: https://stackblitz.com/edit/angular-7ejuyt?file=package.json
If you still face any issues, kindly share the following
details that will be very useful for us to validate further at our end.
- Kindly share the version
of syncfusion packages.
- Kindly share the video
demonstration of the reported issue.
The above details will be very helpful for us to provide a
better solution as soon as possible.
Regards,
Nithya Sivaprakasam.