RB911G-5HPacD scheduler script failed - Hardware problem?

Hello we have many RB911-5HPnD and two new RB911G-5HPacD. We have a simple scheduled script that reboot the boards during the night.

The script works fine with all cards but we have seen that only the RB911G-5HPacD at least every seven days blocking the card and the only way to make it work is the forced reboot.

Some ideas?

Is it running 6.29.1? If not, I would try that first.
Also, can you post the script?

/system ntp client set enabled=yes primary-ntp=193.204.114.232 secondary-ntp=65.55.21.14
/system scheduler add name="system reboot" start-time=03:00:00 interval=1d on-event="/system reboot"

the problem occurs only on board AC and never on RB911-5HPnD.

The ROS is the same on all boards.

cetalfio