5a693e87_Plus__known_issues____RealVNC___Workaround
[ID] 143 [Description] Keys on the computer keyboard's numeric keypad may appear to have no effect, or an unintended effect. [Status] Under consideration. [Workaround] 
The Num Lock key may be out of sync. Disconnect, press the client computer's Num Lock key once, and then reconnect.
VNC® Viewer Plus (known issues) - RealVNC®
Workaround