http://wccftech.com/google-downgrade-pixel-oreo-android-nougat/

You may not be lucky enough to receive Android 8.0 Oreo for the next few months, but Google’s Nexus and now Pixel series is always the first to receive the latest updates. However, after releasing Android 8.0 Oreo to Pixel and Pixel XL, the search giant is apparently sending an update (read: downgrade) to Android Nougat 7.1.2.

Since its official release few weeks back, Google has been having some issues with the OTA releases. The company took its sweet time to release the OTA files and the update was also delayed for some Nexus devices. Looks like the problems continue as some Pixel users have reported receiving a notification to update their phones to Android 7.1.2 Nougat.