I have exaclty the same problem
I've got an ASUS ROG 502VM and my windows key randomly gets "stuck".
It's not physically stuck. This bug just randomly appeared out of nowhere.
I reinstalled Windows, I even downgraded my BIOS, nothing helps. As soon as I get into Windows, it starts
The weird thing is: It just happens IN windows.
So the keys are working perfectly outside of it in the BIOS enviroment and so on. The Key gets virtually stuck after a while, but just in windows.
Even if I let my laptop stand there, doing nothing, the windows key turns on and the only thing that helps is to turn on the virtual keyboard, start an external software, wait until this window appears that says "do you really want to allow changes to be made to your device through this app" (or similar, this is just a tranlsation), THEN I can turn off the windows key with the virtual keyboard and then it works for a few minutes, sometime hours, sometimes seconds...
IT'S SO ANNOYING!!
And it definitely must be a Windows Bug. I already had this bug quite a while ago, then it dissappeard (i guess after an update) and now it appeared again...
Can someone from Microsoft PLEASE check this?