Yet another 5.0 Upgrade problem

I am trying to upgrade my up-to-date UCS 4.4-8 errata1077
I had to remove kopano, the dashboard (which I really hope will come back)

now I see the upgrade note for PostgreSQL-9.4. I followed the link and documentation but there is no mention of a process for a cluster. I have 3 servers. Do I start with the primary/master first?

in these instructions:

“Once the new database / data inventory has been verified, the PostgreSQL 9.4 data can be removed / the software package uninstalled:”

Is the verification automatic or do I need to verify manually?

lastly, I see these issues

The following extensions are incompatible with UCS 5.0:
        cn=zimbra4ucs-udm-syntax,cn=udm_syntax,cn=univention,dc=domain,dc=lan: [unspecified..unspecified)
        cn=guacamole,cn=udm_syntax,cn=univention,dc=domain,dc=lan: [unspecified..unspecified)
        cn=guacamole/config,cn=udm_module,cn=univention,dc=domain,dc=lan: [unspecified..unspecified)
        cn=59univention-radius,cn=ldapacl,cn=univention,dc=domain,dc=lan: [unspecified..unspecified)
        cn=66univention-radius,cn=ldapacl,cn=univention,dc=domain,dc=lan: [unspecified..unspecified)

is it safe just to remove these entries?

ldapdelete -x -D "cn=admin,$(ucr get ldap/base)" -y /etc/ldap.secret “cn=xxxxxx,cn=xxxx,dc=domain,dc=lan”

Thank you… diagnotics all pass, no problems detected.

I went ahead and created backup images of each server, then removed the incompatible extensions, and upgraded postgresql to 9.6.23 on two of the three servers.

but it appears there is a permissions issue with folder in /var/univention-backup/update-to-5.0-0

I do have this folder mounted as an NFS mount as the backups were taking up too much disk space. All three servers have an fstab entry mapping /var/univention-backup to their own folder on a 25TB storage array.
eg: /var/univention-backup nfs rsize=8192,wsize=8192,timeo=14,intr

this is the first time this issue has happened during an upgrade. I see the created permissions on the folder do not match the permissions on the previous folders.

drwxr-xr-x  2 nobody nogroup   4096 Apr 10  2020 update-to-4.4-4
drwxr-xr-x  2 nobody nogroup   4096 Jul 14  2020 update-to-4.4-5
drwxr-xr-x  2 nobody nogroup   4096 Sep 24  2020 update-to-4.4-6
drwxr-xr-x  2 nobody nogroup   4096 Jan 16  2021 update-to-4.4-7
drwxr-xr-x  2 nobody nogroup   4096 May 17 19:26 update-to-4.4-8
drwx------  2 nobody nogroup   4096 Oct 30 13:53 update-to-5.0-0

the relevant log entry from updater.log:

Checking tls_public_key_size ...                  OK
Checking tls_public_key_size_ucs-sso ...          OK
Checking usr_mountpoint ...                       OK
Checking valid_machine_credentials ...            OK
install: cannot change owner and permissions of ‘/var/univention-backup/update-to-5.0-0’: Operation not permitted ERROR: Could not create /var/univention-backup/update-to-5.0-0
Error: Update aborted by pre-update script of release 5.0-0
exitcode of univention-updater: 1
ERROR: update failed. Please check /var/log/univention/updater.log

the easiest test was to unmount the NFS folder and leave /var/univention-backkup/ on the local storage. The upgrade continued without further issue.

I am not an expert in NFS and this was the first time this issue has happened across many upgrades over the years. Does anyone have an idea why this would have occoured?