XPS 15 9560 Keyboard Issue - Some Keys Don't Work

On this 2-year old machine the keyboard is inconsistent. Sometimes a few of the keys like the G key or the left-side Control key and the up arrow key stop working. If I press those keys nothing happens. Or, in some cases, if I press the G key I'll get a G character plus another random letter.

As I wrote, it's not consistent. Sometimes when rebooted, the keyboard will work correctly, other times it will not. I don't see any pattern, seems random.

An external, USB keyboard works fine as does the on-screen keyboard.

I have run the Dell diagnostics and it reports no problems.

I have updated all the drivers and BIOS.

I have replaced the physical keyboard with a new one.

Any thoughts?