I've had the same issue with my XPS 15z since I opened the box. I never had McAfee and hadn't loaded any Security SW when I first began to experience the issue. I initially though it was a driver
issues (based on some other forums) with my Cypress touchpad but after changing multiple driver versions I've had no luck.
Symptoms sound similar...active window loses focus and doesn't seem to go anywhere. It doesn't matter what my active program is (Chrome, Word, Pinnacle Studio, etc.) even with a blank desktop I'll notice that the active highlighted desktop icon will lose focus.
This occurs when I'm using the computer, and ALSO occurs when I'm not touching or interacting with the computer in any way.
No background apps being updated, not AV scans running, just Poltergeist behavior.