After troubleshooting, we suspect that the issue is with the motherboard of the laptop. This would explain intermittent issues between the display, backlight, keyboard, and touchpad (as they all interconnect at the motherboard). We advised that the customer use an external display, keyboard, and mouse for now, call their corporate IT department to assist with data backup, and have a new computer sent to them rather than replace the motherboard per se, as that would require in-depth cooperation with their IT department in ways we don't have access to.