We are aware of the issue and it is in our backlog, but unfortunately I cannot commit to a specific time frame when it will be fixed. For now, I could suggest you to follow this feedback item
in order to be notified about any related changes.
As a partial workaround, you could change the text rendering mode of RadRichTextBox to the classic (an a little slower) one:
.radRichTextBox.TextRenderingMode = TextBlockRenderingMode.TextBlockWithPropertyCaching;
Please, excuse us for the inconvenience. Do not hesitate to contact us if you have other questions.
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