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:
"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.