Check device manager, possibly look for into a firmware upgrade. It seems your USB input devices are either losing connectivity or priority for some reason or another.
You might also check Event Logs to see if there's any errors occurring during the time you're gaming and this issue happens.
I would look at updated drivers, firmware upgrades, you might even try loading optimized defaults in your UEFI/BIOS to see if that resolves any issues. If you're on 10 and you're running EHCI compatability for Windows 7, that shouldn't cause issues...but could be.
Have you tried different USB ports? Try USB 2.0 ports, try front panel ports, etc.
When this occurs, and you press Alt+Tab can you change what application you are "focusing" on?
I did read somewhere with a user on Win10 that had a similar issue, had to change their input language to English-US to resolve it.
Another thing to look at is power saving for USB, though honestly that shouldn't cause issues here it very well could be.