Pixel 2 xl unroot question

[Android Central Question]

Hi i unrooted my pixel 2 xl by installing the factory image. But when I try to lock the bootloader back up the phone says there is no operating system. So I unlock the bootloader and it boots right back up to the setup wizard. I understand the reasoning for that. Just wondering why I'm not able to lock the bootloader again? Or why it says no operating system? Any help would be great. Thanks.