BBB always decline VPN ip when running dhclient in system service

[zero88]

Describe the bug

BeagleBone decline new VPN IP constantly when invoked dhclient in unix service

Jun  7 15:04:35 beaglebone dhclient[2311]: DHCPDISCOVER on vpn_bp to 255.255.255.255 port 67 interval 3
Jun  7 15:04:35 beaglebone dhclient[2311]: DHCPOFFER of 10.0.0.2 from 10.0.0.1
Jun  7 15:04:35 beaglebone dhclient[2311]: DHCPREQUEST for 10.0.0.2 on vpn_bp to 255.255.255.255 port 67
Jun  7 15:04:35 beaglebone dhclient[2311]: DHCPACK of 10.0.0.2 from 10.0.0.1
Jun  7 15:04:35 beaglebone dhclient[2311]: DHCPDECLINE of 10.0.0.2 on vpn_bp to 255.255.255.255 port 67

Version

connmand: v1.36
dhclient: isc-dhclient-4.4.1

To Reproduce
Steps to reproduce the behavior

Additional context

It works fine if after restart vpn service then trigger dhclient manually. For example:

dhclient --no-pid -v -nw vpn_zbb