The latest XL variant of the Pixel smartphone series may be susceptible to a fault in which the glass rear panel may spontaneously start to come away from the rest of the phone. This same problem has now been reported multiple times by different Redditors. Google has yet to publicly respond in relation to this new issue with its devices.
https://www.notebookcheck.net/Several-Pixel-4-XL-users-complain-the-glass-rear-panel-is-peeling-off-their-phones.482319.0.html