1) Unlock bootloader
2) Flash custom recovery
3) Root your phone
4) Boot into recovery and restore from there
5) Reboot your phone to see if the problem is solved.
If the problem that you were facing is solved then
6) Full unroot you device
7) Reflash stock recovery
8) Relock the bootloader *
Done! And now, you will be able to install the OTA updates .
*If you are not rooted and have stock recovery in your phone already, I don't think locking your bootloader is necessary to install the OTA updates.
Please "thumbs up" if I helped.