Hi Mike,
unfortunately this is an issue with Microsoft’s RDP ActiveX control which ships with Windows and is used by Royal TS. You can read more about that here:
You can download and try RDCM from Microsoft here (which uses the same ActiveX):
https://www.microsoft.com/en-us/download/details.aspx?id=44989
You will notice a similar behavior.
All you can do is to report he issue to Microsoft (as mentioned in the linked KB article above using the Feedback Hub tool) and hope they will fix that soon.
Regards,
Stefan