i don’t personally own an xps, I’ve read that there is a problem with their 4k screens and people are returning them to get something else.
that being said, i believe its an issue with the gui graphics driver because the screen can refresh video just fine. you can mess around with nvidia program settings and force premiere.exe to use compatibility mode as primary video card, or mess with the refresh rate etc(just a guess). down the road there may be driver/firmware updates from dell, but its probably easier to return it.