router was rebooted without proper shutdown by watchdog time

Hello,
I have omnitik U-5HnD that can’t work for more than 24h.
Firmware is updated, router os too. Cpu usage is less than 10%, this device work as bridge and ap.

Every time it reboots I get this in log:
router was rebooted without proper shutdown by watchdog timer

I disabled once a watchdog timer and router freezes so I had to switch off power.
Watchdog is using default configuration.

What should I do?