I just tried locking the bootloader to be greeted with “Your device is corrupt. It can’t be trusted and will not boot” as well.
I used IMG-e-2.7-t-20250111460957-official-FP5.zip to flash and made sure the security patch dates where at least the same if not higher on the e/os build. they where both January 5.
I can still unlock and reflash though. But I’d like to fully lock the phone if possible.