Hi Mohamed,
Thank you for contacting Syncfusion support.
The reported issue is working as expected from our side. We have prepared a sample based on the mentioned details, which can be downloaded from the below link.
Kindly, provide us more details about the issue reproducing scenario, SfRichTextEditor NuGet version used at your end or please modify the provide the provided sample, which will be helpful for us to provide an appropriate solution at earliest.
Regards,
Devaraj S