The bond NIC does not up when reboot system in ubuntu 16.4

Hi folks,
As the title says,
When I using two physical network card to set the bonding NIC, random reboot system will meet the bond NIC didn't stand up and the two physical NICs are down status too. The number of restarts is 345 times that failed approximately 30 times.

Why, and how to solve it?
Any help will be appreciated, Thanks.

Following are some information for reference.

#1. System version,
root@ubuntu:~# uname -a
Linux ubuntu 4.4.0-62-generic #83-Ubuntu SMP Wed Jan 18 14:10:15 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux
root@ubuntu:~# cat /etc/issue
Ubuntu 16.04.2 LTS \n \l

root@ubuntu:~#

#2. automation reboot shell script that will weld to rc.local file

sleep 2m
ip a >> /root/inter_info
echo `date` >> /root/inter_info
echo "\n" >> /root/inter_info
reboot

#3. inter_info log
root@ubuntu:~/log-0815# cat inter_info | grep bond0 |wc -l
345
root@ubuntu:~/log-0815# cat inter_info | grep DOWN |grep bond0 |wc -l
30
root@ubuntu:~/log-0815#
root@ubuntu:~/log-0815# cat inter_info | grep DOWN |grep ethx0 |wc -l
30
root@ubuntu:~/log-0815#
root@ubuntu:~/log-0815# cat inter_info | grep DOWN |grep ethx1 |wc -l
30
root@ubuntu:~/log-0815#