Windows 10 Alt+Tab task switcher gets stuck

In Windows 10 there is an alternate version of Alt+Tab which you get if you press Ctrl+Alt+Tab. Give it a try. Note that letting go of the keys doesn't activate the selected window. You have to hit Space or Enter in order to accept your choice.

My Windows 10 VMs have all begun acting as if I've pressed Ctrl+Alt+Tab when I've only pressed Alt+Tab. I have to hit space or enter to complete every Alt+Tab even though I am not pressing Ctrl.

I opened the "On-Screen Keyboard" utility which comes with Windows 10, and when I press Alt+Tab I sometimes can see the briefest flash of the Ctrl key appearing even though I have not pressed it. At other times, it shows the Ctrl key being stuck down even when I'm not pressing any keys. It appears that Parallels or macOS are temporarily sending the Ctrl key to Windows.

Is this a known issue, or can anyone suggest a workaround? It's a little thing, but it quickly becomes maddening when I use Alt+Tab hundreds of times every day.

• Parallels: 15.1.0 (47107)
• Host: macOS Mojave 10.14.6
• Guest: Windows 10 18362.418, Windows 10 18362.356

 

It appears that this is because I am using a PC keyboard which sends right Alt instead of left Alt. I found the difference by installing an app that shows me what scan codes the keyboard sends:

• https://apps.apple.com/us/app/key-codes/id414568915?mt=12

As it turns out, in newer versions of Winodws the Right Alt+Tab combination works the same as Ctrl+Alt+Tab.
If I use a Mac keyboard the problem doesn't happen unless I press the right-side Alt key when pressing Tab.
Presumably I could fix this by editing my registry to remap Right Alt as Left Alt on each Windows machine. It would be great if there's a way to fix this using Parallels instead though. I doubt I'm the only user who will run into this.