Mikrotik L009 Users uptime reset to 0 after power outage or reboot

Good Day i have a Mikrotik L009 users uptime always reset to 0 when the mikrotik router reboot or if there is a power outage plz help on how to fix this, 4 hrs voucher can last up to 3 days beacuse if users use 3 hrs out of the 4 hrs and the mikrotik reboot then his time will rest to fresh 4 hrs

buy a ups and make it not reboot

Thank you i thougt i can configure auto backup or something like that to backup the users uptime regularly