No communication between the DNS/DHCP Manager Console and OES server (status,start,stop)

The screenshot shows the tab "DHCP (OES Linux)" in the DNS / DHCP Manager console
in the bottom of the image it shows the state of the DHCP servers.


The dhcp service is started on all these servers

You can see that the status is known only for four servers.
The button "start/stop DHCP service" works fine on this servers and
the dhcp service can be canceled and also restarted

But the status of the "dhcp service" is not recognized for all the other DHCP servers
and so we can not start or stop dhcp service on these servers.

All servers were installed at different times (last three years) with OES11 and
are upgraded to OES11SP2 with all patches.

The server keto (DHCP_keto) is a new installation OES11SP2 few days ago.
All OES servers were set up identically from me. LDAP, LUM, DMS, DHCP works fine.

Which service on the OES server is responsible for
communication (status indicator) between the DNS/DHCP Manager and the OES serve?
How the status query is performed by the DNS/DHCP Manager?
How can I test the communication to the server on the client (console)?
Which configurationfiles I should be compare on the server?

Thanks in advance