Hi,
I am having the same / similiar issue.
I have had Zammad running for close to 12 months and had no issue.
I have just noticed that zammad is not syncing with my LDAP server (AD).
I am seeing the below error message come up.
I have logged in via ssh and the i can ping the name without any problem and i am connected to the ldap service on other systems without any other problem.
UBUNTU 22.04
Zammad version 6.1.0-1699563276.d63911c3.jammy