Hello, @Geoffrey F4FXLyou just saved me a lot of debugging time. I have multiple orange pi zero with h2+ and h3 and I had the same problem as you. With the reboot command, the sbc shutsdown but doesn't boot again, i need to reset the power for getting it booting again. On my side , this command extraargs=reboot=warm didn't worked but extraargs=reboot=watchdog worked perfectly. I just rebooted it 5 times in a row and it always rebooted well.
My version : v25.11.2 for Orange Pi Zero running Armbian Linux 6.12.58-current-sunxi