[Samba] samba AD-DC with bind9, dyn-dns complains that "No AD dhcp user exists"

[Carlos Jesus]

Hi all, once again I ask for your help since I'm out of ideas. First my
setup.
Two DC's running Debian buster and samba 4.12.11 with bind9, and dynamic
dns through dhcp (in failover mode) using the wiki script. One of the DC's
is physical, the other is virtual (Proxmox).
Both DC's have very similar configurations (but we all have heard this a
thousand times...) and on the physical DC all is well, let's forget about
it.
On the virtual DC, I get the error "No AD dhcp user exists" blablabla. If I
run the suggested commands (kinit Administrator at SAMDOM.EXAMPLE etc), it
complains that the user already exists which can be confirmed by wbinfo
-u|grep dhcpduser.
The dhcp server is working since I get things like
DHCPINFORM from 192.168.1.147 via br0
DHCPACK to 192.168.1.147 (00:13:72:40:50:6a) via br0
execute: /usr/local/bin/dhcp-dyndns.sh exit status 256
Unfortunatly I don't know what "exit status 256" is
Now:
1) /etc/dhcpd.keytab exists and with right permissions (root:root
r--------)
2)bind9 is up and running
3) /etc/resolv.conf
options rotate timeout:5
search SAMDOM.EXAMPLE
nameserver 192.168.1.150
nameserver 192.168.1.149
4) Running TESTUSER="$(wbinfo -u | grep 'dhcpduser')" returns
SAMDOM/dhcpduser (as expected, so why does the script thinks TESTUSER is
empty?)
I can provide dhcpd.conf, named.conf and smb.conf however, they are very
simillar on both DC's.

Any ideas?
Best regards

Carlos