The Pixel 5 looks to be suffering from a manufacturing defect that leaves a gap between the phone's display and side rail.
Several reports on Google's Pixel Phone Help forum and the XDA Forums have shown multiple instances of the screen coming away from the body, with the most common location being around the top left corner of the phone. Needless to say, this isn't something you want to find in a brand new flagship phone.
What's worse is that users are reporting this problem from the moment they unbox the phone. So it looks like Google can't even blame poor user care or wear and tear for this.
Another factor which makes this problem all the more frustrating is that the Pixel 5 is supposedly IP68 rated for water and dust resistance. Having a big gap like this on the handset would certainly invalidate that rating, since it looks large enough to let water or dust enter the body of the phone and cause major damage.
The Pixel 5 is still new, and has only barely made its way out to the first wave of pre-order customers. We'll have to wait and see if teardown videos reveal what the problem is, or if Google makes an official statement on the matter.
We were quite impressed by Google's phone in our Pixel 5 review, particularly with the cameras, battery life and software. We also complimented the well-sized 5.8-inch design of the handset, but perhaps that needs to be reconsidered in light of this new problem.