I can confirm that this happened to me too, exactly like this, and just today. Just before doing windows updates, it worked, and as soon as I did windows updates on the host machine, it no longer worked. The KB4522742 already existed on the remote machine since Nov 20.
On the remote machine, CTRL, Shift, Enter do not work.
(Thus, cannot CTRL-C / CTRL-V, cannot shift-arrow keys for highlighting, and Enter doesn't work, both of them - on the main keyboard, and the enter key in the num pad).
I am attaching a screenshot of the Windows Updates. The updates that were installed were these two:
TWO Microsoft Office "Click-to-Run Update Support".
"October 24, 2019-KB4522742 Cumulative Update for .NET Framework 3.5 and 4.8 for Windows 10, version 1909 and Windows Server, version 1909".
I hope that helps to figure out the issue.
EDIT: I am using the latest Remote Utilities on both machines 184.108.40.206.
Edited:Alex Shaw - Dec 18, 2019 4:34:43 pm EST