Odhcp6c do "bound" operation with an empty $ADDRESSES occasionally

Installing and Using OpenWrt Network and Wireless Configuration
1

My wan interface use pppoe protocol. Sometimes the wan_6 interface just can't get its ipv6 address.
odhcp6c -s /lib/netifd/dhcpv6.script -P0 -t120 pppoe-wan

So I add some code in /lib/netifd/dhcpv6.script to see the problem:


echo "$2" >>/tmp/odhcp6c.log
case "$2" in
        bound)
                teardown_interface "$1"
                setup_interface "$1"
        ;;
        informed|updated|rebound)
                setup_interface "$1"
        ;;
        ra-updated)
                [ -n "$ADDRESSES$RA_ADDRESSES$PREFIXES$USERPREFIX" ] && setup_interface "$1"
        ;;
        started|stopped|unbound)
                teardown_interface "$1"
        ;;
esac

[ -z "$ADDRESSES" ] &&  echo "empty addr" >> /tmp/odhcp6c.log
        [ -z "$ADDRESSES" ] &&  { setsid ifup wan; exit; }
        for entry in $ADDRESSES; do
                local addr="${entry%%/*}"

After trying a few times, here is the outcome:

started
bound
Tue May 13 14:49:51 HKT 2025 setup_interface
Tue May 13 14:49:51 HKT 2025 addresses: 
empty addr
stopped
started
bound
Tue May 13 14:50:17 HKT 2025 setup_interface
Tue May 13 14:50:17 HKT 2025 addresses: 
empty addr
stopped
started
bound
Tue May 13 14:50:33 HKT 2025 setup_interface
Tue May 13 14:50:33 HKT 2025 addresses:  240e:3b0:d046:57:d92a:e86d:bdf8:a84c/64,172799,259199
Tue May 13 14:50:33 HKT 2025 240e:3b0:d046:57:d92a:e86d:bdf8:a84c 64 172799 259199
ra-updated
Tue May 13 15:06:40 HKT 2025 setup_interface
Tue May 13 15:06:40 HKT 2025 addresses:  240e:3b0:d046:57:d92a:e86d:bdf8:a84c/64,172799,259199
Tue May 13 15:06:40 HKT 2025 240e:3b0:d046:57:d92a:e86d:bdf8:a84c 64 172799 25919

I also try to dump the icmpv6 packets on pppoe interface, but eveytime odhcp6c is restarted, the pppoe interface also will be restarted, and then tcpdump stop works.

Any suggestions are welcome, thank you!