I don't know a ton about this but can't you just flash the stable/release OTA image? Google says this can be done without unlocking or losing your data:
https://developers.google.com/android/ota
"This page contains full OTA update packages that allow you to restore your Nexus or Pixel device's original factory firmware. You will find these files useful if you have experienced a failure to take an OTA. This has the same effect as flashing the corresponding factory image, but without the need to wipe the device or unlock the bootloader."
I may be missing something tho. I haven't personally tried this.