Bind9 and samba4 services do not start after upgrade from UCS 4.4.8 / 1118 to 5.0.0

Hello,
I have a problem after UCS Upgrade from 4.4.8 errata 1118 to UCS 5.
I have two UCS server: one is our dc, the second is backup-system.
Before the upgrade I checked all services, system diagnosis, latest version on both systems: everything was fine.
I had to uninstall two apps (not supported on UCS 5), after long time waiting both servers were on UCS 5.0.0.
I check the services, ran the system diagnosis: everything was fine on both systems.
After that I looked for package updates and started to update the dc to version 5.0.0 errata 164 (more then 200 packages). I got the message “please reboot” - and then the bind9 and samba4 service did not start anymore.

sudo systemctl status bind9.service
● bind9.service - BIND Domain Name Server with samba4 backend
   Loaded: loaded (/lib/systemd/system/bind9.service; enabled; vendor preset: enabled)
  Drop-In: /etc/systemd/system/bind9.service.d
           └─10-configure-backend.conf
   Active: failed (Result: signal) since Sat 2021-12-04 19:27:06 CET; 23s ago
     Docs: man:named(8)
  Process: 19889 ExecStart=/usr/lib/univention-bind/samba4 start (code=killed, signal=SEGV)
  Process: 19890 ExecStartPost=/usr/lib/univention-bind/samba4 wait-for-startup (code=exited, status=124)
 Main PID: 19889 (code=killed, signal=SEGV)

Dez 04 19:26:59 dc samba4[19890]: rndc: connect failed: 127.0.0.1#953: connection refused
(...in summary 7 times that line...)
Dez 04 19:27:06 dc systemd[1]: bind9.service: Control process exited, code=exited, status=124/n/a
Dez 04 19:27:06 dc systemd[1]: bind9.service: Failed with result 'signal'.
Dez 04 19:27:06 dc systemd[1]: Failed to start BIND Domain Name Server with samba4 backend.

The same on backup-system

sudo service bind9 status
● bind9.service - BIND Domain Name Server with samba4 backend
   Loaded: loaded (/lib/systemd/system/bind9.service; enabled; vendor preset: enabled)
  Drop-In: /etc/systemd/system/bind9.service.d
           └─10-configure-backend.conf
   Active: active (running) since Sat 2021-12-04 18:18:10 CET; 1h 12min ago
     Docs: man:named(8)
  Process: 991 ExecStartPost=/usr/lib/univention-bind/samba4 wait-for-startup (code=exited, status=0/SUCCESS)
 Main PID: 990 (named)
    Tasks: 7 (limit: 4665)
   Memory: 67.3M
   CGroup: /system.slice/bind9.service
           └─990 /usr/sbin/named -c /etc/bind/named.conf.samba4 -f -d 0

and the 7 lines with errors on dc show here information about the configuration (but instead of “dc samba4[19890]” there is now “backup-system named[990]”) .

So I tried
sudo /usr/sbin/named -c /etc/bind/named.conf.samba4 -f -d 0
on dc and got the error “Speicherzugriffsfehler”.
I looked for further information and got

journalctl -xe
(...)
Dez 04 19:42:33 dc kernel: isc-worker0000[26187]: segfault at 8 ip 1122334455667788 sp 9900aabbccddeeff error 4 in ld-2.28.so[7f5c64ef8000+1

followed by a line with code.

What can I do so I can start both bind9 and samba4 services?

After update to version 5.0.1 errata 187 samba4 starts without problems, bind9 has to start manually (automatic start fails). But there are some new errors when running system diagnosis: letsencrypt reports failing signed_chain (old “friend”) and the following samba replication error

samba-tool drs showrepl gibt ein Problem mit der Replikation zurück.
In eingehend b’CN=Schema,CN=Configuration,DC=abc,DC=here-is-our-domain-name,DC=de’: Fehler während der DRS Replikation von Default-First-Site-Name/NAME-OF-BACKUP-SYSTEM (WERR_GEN_FAILURE).
In eingehend b’DC=DomainDnsZones,DC=abc,DC=here-is-our-domain-name,DC=de’: Fehler während der DRS Replikation von Default-First-Site-Name/NAME-OF-BACKUP-SYSTEM (WERR_GEN_FAILURE).
In eingehend b’DC=abc,DC=here-is-our-domain-name,DC=de’: Fehler während der DRS Replikation von Default-First-Site-Name/NAME-OF-BACKUP-SYSTEM (WERR_GEN_FAILURE).
In eingehend b’CN=Configuration,DC=abc,DC=here-is-our-domain-name,DC=de’: Fehler während der DRS Replikation von Default-First-Site-Name/NAME-OF-BACKUP-SYSTEM (WERR_GEN_FAILURE).
In eingehend b’DC=ForestDnsZones,DC=abc,DC=here-is-our-domain-name,DC=de’: Fehler während der DRS Replikation von Default-First-Site-Name/NAME-OF-BACKUP-SYSTEM (WERR_GEN_FAILURE).
In ausgehend b’CN=Schema,CN=Configuration,DC=abc,DC=here-is-our-domain-name,DC=de’: Fehler während der DRS Replikation nach Default-First-Site-Name/NAME-OF-BACKUP-SYSTEM (WERR_GEN_FAILURE).
In ausgehend b’DC=DomainDnsZones,DC=abc,DC=here-is-our-domain-name,DC=de’: Fehler während der DRS Replikation nach Default-First-Site-Name/NAME-OF-BACKUP-SYSTEM (WERR_GEN_FAILURE).
In ausgehend b’DC=abc,DC=here-is-our-domain-name,DC=de’: Fehler während der DRS Replikation nach Default-First-Site-Name/NAME-OF-BACKUP-SYSTEM (WERR_GEN_FAILURE).
In ausgehend b’CN=Configuration,DC=abc,DC=here-is-our-domain-name,DC=de’: Fehler während der DRS Replikation nach Default-First-Site-Name/NAME-OF-BACKUP-SYSTEM (WERR_GEN_FAILURE).
In ausgehend b’DC=ForestDnsZones,DC=abc,DC=here-is-our-domain-name,DC=de’: Fehler während der DRS Replikation nach Default-First-Site-Name/NAME-OF-BACKUP-SYSTEM (WERR_GEN_FAILURE).

Some searching on the univention sites brought the solution of the samba problem Problem: samba-tool drs showrepl shows WERR_GEN_FAILURE - many many thanks!