pfSense

'DHCPv6 Static Mappings for this Interface' option isn't reliable working (2.5.2-RELEASE (amd64))

I am experiencing the same behaviour as discribed in Bug #8717.

My setup is a little bit different. I my got /56 IPv6 Range via prefix delegation. On the interfaces I use "Track interface" with /64 . On 2 of 3 interfaces the Static Mapping works. On one Interface is a Pi 4 with Raspian OS and on the other Debian 10 machine with network-manager. The third interface is also a Debian 10 machine with network-manager, but can't get this machine a static IP. As static entry I use PREFIX::a:1. The DHCP range is PREFIX::d:1111 - PREFIX::d:ffff.

cat /var/dhcpd/etc/dhcpdv6.conf

correctly shows the static entry that I want:

option domain-name "localdomain";
option ldap-server code 95 = text;
option domain-search-list code 119 = text;

default-lease-time 7200;
max-lease-time 86400;
log-facility local7;
one-lease-per-client true;
deny duplicates;
ping-check true;
update-conflict-detection false;
authoritative;
subnet6 2a02:8106:26:c205::/64 {
    range6 2a02:8106:26:c205::d:1111 2a02:8106:26:c205::d:ffff;
    do-forward-updates false;
    #option dhcp6.name-servers --;

}
host s_opt6_0 {
    host-identifier option dhcp6.client-id 00:01:00:01:29:0d:aa:ac:d0:50:99:76:7d:6b;
    fixed-address6 2a02:8106:26:c205::a:1 ;
    option host-name nextcloud;
}

But the output of

$ sudo dhclient -6 -r eth0
$ sudo dhclient -6 eth0

shows

Killed old client process
Internet Systems Consortium DHCP Client 4.4.1
Copyright 2004-2018 Internet Systems Consortium.
All rights reserved.
For info, please visit https://www.isc.org/software/dhcp/

Listening on Socket/eth0
Sending on   Socket/eth0
XMT: Forming Release, 0 ms elapsed.
XMT:  X-- IA_NA 99:76:7d:6b
XMT:  | X-- Release Address 2a02:8106:26:c205::d:2fcc
XMT:  V IA_NA appended.
XMT: Release on eth0, interval 920ms.
Internet Systems Consortium DHCP Client 4.4.1
Copyright 2004-2018 Internet Systems Consortium.
All rights reserved.
For info, please visit https://www.isc.org/software/dhcp/

Listening on Socket/eth0
Sending on   Socket/eth0
PRC: Soliciting for leases (INIT).
XMT: Forming Solicit, 0 ms elapsed.
XMT:  X-- IA_NA 99:76:7d:6b
XMT:  | X-- Request renew in  +3600
XMT:  | X-- Request rebind in +5400
XMT:  | X-- Request address 2a02:8106:26:c205::d:2fcc.
XMT:  | | X-- Request preferred in +7200
XMT:  | | X-- Request valid in     +10800
XMT: Solicit on eth0, interval 1050ms.
RCV: Advertise message on eth0 from fe80::ec4:7aff:feac:791a.
RCV:  X-- IA_NA 99:76:7d:6b
RCV:  | X-- starts 1635453106
RCV:  | X-- t1 - renew  +0
RCV:  | X-- t2 - rebind +0
RCV:  | X-- [Options]
RCV:  | | X-- IAADDR 2a02:8106:26:c205::d:2fcc
RCV:  | | | X-- Preferred lifetime 4500.
RCV:  | | | X-- Max lifetime 7200.
RCV:  X-- Server ID: 00:01:00:01:29:0d:ae:78:0c:c4:7a:ac:79:1a
RCV:  Advertisement recorded.
PRC: Selecting best advertised lease.
PRC: Considering best lease.
PRC:  X-- Initial candidate 00:01:00:01:29:0d:ae:78:0c:c4:7a:ac:79:1a (s: 10103, p: 0).
XMT: Forming Request, 0 ms elapsed.
XMT:  X-- IA_NA 99:76:7d:6b
XMT:  | X-- Requested renew  +3600
XMT:  | X-- Requested rebind +5400
XMT:  | | X-- IAADDR 2a02:8106:26:c205::d:2fcc
XMT:  | | | X-- Preferred lifetime +7200
XMT:  | | | X-- Max lifetime +7500
XMT:  V IA_NA appended.
XMT: Request on eth0, interval 1090ms.
RCV: Reply message on eth0 from fe80::ec4:7aff:feac:791a.
RCV:  X-- IA_NA 99:76:7d:6b
RCV:  | X-- starts 1635453107
RCV:  | X-- t1 - renew  +0
RCV:  | X-- t2 - rebind +0
RCV:  | X-- [Options]
RCV:  | | X-- IAADDR 2a02:8106:26:c205::d:2fcc
RCV:  | | | X-- Preferred lifetime 4500.
RCV:  | | | X-- Max lifetime 7200.
RCV:  X-- Server ID: 00:01:00:01:29:0d:ae:78:0c:c4:7a:ac:79:1a
PRC: Bound to lease 00:01:00:01:29:0d:ae:78:0c:c4:7a:ac:79:1a.

which is a IP out of the DHCP pool. Also

$ sudo nmcli con down eth0
$ sudo nmcli con up eth0

does not lead to success.