Clearly if same issue in other OS, it’s not Creator Update…
Maybe you can try to open the keyboard (no screw it seems to be clipped together) and press a little inside if it is just a “false contact” it may solve it…
note that you mostly risk to completely break the keyboard doing so…
Already fresh installed windows 10 anniversary update on my mixplus. Still the same issue. I have opened up the keyboard, but dont have any idea where to inspect. Most probably need to buy a new unit.