Dell XPS 15 7590 missing keystrokes

There are one or two older messages on this subject for the XPS laptop but I'm posting here because my fix was a bit different. For me, it was an easy fix. 

Symptom: on a brand new XPS 15 7590 right out of the box, not all keystrokes were registering on the keyboard as I typed. An average of 1 out of every 10 keys would fail to register. The problem did not depend on how fast I was typing and it affected random keys. However, an external USB keyboard worked fine. Running Dell update did not fix the problem. 

The problem appears to have been related to the NVIDIA display driver, or lack thereof. I knew that my laptop was supposed to have an NVIDIA display card, but as delivered, there was no sign of it. Device Manager > Display adapters only listed Intel, and right-mouse-button clicking on the desktop showed no NVIDIA control panel in the pop-up menu. 

I updated/reinstalled the BIOS. The BIOS can be updated via the Support tab, selecting your model, selecting Drivers and Downloads, then searching for BIOS. In the list for me, there is "Dell XPS 15 7590 System BIOS URGENT". After downloading this and running the update, and rebooting, the NVIDIA display driver appeared in Device Manager and the NVIDIA control panel appeared when I right-mouse-button click on the desktop. This fixed the keystroke problem for me.