I have logged it in our feedback portal by making this thread public. You can track its progress, subscribe for status changes and add your comments on the following link - feedback item.
I have also updated your Telerik points.
Unfortunately, the issue is at a location that is too deep in the RadPdfViewer's functionality for any customization to have effect on it. We will do our best to introduce a fix as soon as possible. Please excuse us for the inconvenience caused.
I hope this information helps. If you need any further assistance please don't hesitate to contact me.