After updating to 2.5 I got WAN_DHCP6 Stuck Pending / Unknown again

[MarcO42]

Hi @all,
I'm not able to find any newer thread about this topic then this one:

Re: WAN_DHCP6 Stuck Pending / Unknown

I updated from 2.4.5 to 2.5 and all is great...only the gateway shows Pending.
If I manually add a monitoring ip (like some for Cloudflare) it works. But then its not monitoring and showing my ip.
In the dhcp log I got this for dhcpv6:

Feb 24 03:50:04 router dhcp6c[39160]: Start address release
Feb 24 03:50:04 router dhcp6c[39160]: Sending Release
Feb 24 03:50:04 router dhcp6c[39160]: failed to remove an address on pppoe0: Can't assign requested address
Feb 24 03:50:04 router dhcp6c[39160]: Start address release
Feb 24 03:50:04 router dhcp6c[39160]: Sending Release
Feb 24 03:50:04 router dhcp6c[39160]: remove an address 2a04:1111:6c0d:5d00:20d:b9ff:fe42:61c2/64 on igb2
Feb 24 03:50:05 router dhcp6c[39160]: Sending Release
Feb 24 03:50:05 router dhcp6c[39160]: Sending Release
Feb 24 03:50:15 router dhcpleases[6619]: Sending HUP signal to dns daemon(71026)
Feb 24 03:50:17 router dhcp6c[19627]: failed to open /usr/local/etc/dhcp6cctlkey: No such file or directory
Feb 24 03:50:17 router dhcp6c[19627]: failed initialize control message authentication
Feb 24 03:50:17 router dhcp6c[19627]: skip opening control port
Feb 24 03:50:18 router dhcp6c[20356]: Sending Solicit
Feb 24 03:50:19 router dhcp6c[20356]: Sending Request
Feb 24 03:50:19 router dhcp6c[20356]: dhcp6c Received REQUEST
Feb 24 03:50:19 router dhcp6c[20356]: add an address 2a04:1111:6c1f:c800:20d:b9ff:fe42:61c2/64 on igb2
Feb 24 03:50:19 router dhcp6c[20356]: add an address 2a04:1111:6c00:99::add/128 on pppoe0

I have no clue how to debug or fix this issue. Maybe someone can help me to find a solution?
Many thx
Marco