Let's do this a different way, then. Install this addon:

https://www.dropbox.com/s/pjmpsvguwogqmo8/keyTest-0.1.nvda-addon?dl=1

That will add a Key test item to the NVDA Tools menu. Activate it, then
hit that key a few times and see what it says. Your keyboard will return
to normal 15 seconds later.