My Mid 2014 Macbook Pro has the exact same symptom — the right command key and the zero key intermittently don’t work.
Watching with the Keyboard Viewer, I have found that they (so far) will respond after some time if I simply keep them pressed down and just wait. In anywhere from 30-300 seconds, the keys seem to come back to life for a while so long as I keep using them. Once I stop using the keys for while, I have to press and hold and wait again.
Leads me to think the issue may be temperature-related as the only physical change of keeping those keys pressed is my fingers absorbing some heat.
Glad I didn’t try the upper case fix, thanks Kjell…that was next on my list! I tried the NVRAM reset, no luck too.