That's a known bug.
Yes I did flash dtbo and vendor_boot just like the instructions. Worked without problems
Just follow the instructions and you should be fine. Be aware that when you adb sideload the rom, two messages will pop up saying that the signature verification failed and you will downgrade your system just confirm both messages with yes and then wait a bit (took like 2-3min after the confirmation to finish) and you should be good.
Battery backup and performance improved and new oos camera ui. Battery backup much better then oos 12 fw base builds