I have just tested the reboot command using CLI and my router rebooted successfully. Could you provide a screenshot of your router logs once you enter the reboot command?
Regarding keep all settings feature, I have noticed that you have the latest firmware version installed already. Are you reflashing it to the older version? It could be that settings cannot be kept installing older firmware that the current installed.
Also, I would suggest to try to restore your router to the factory default configuration and test all these features again.