Make sure you really updated all DHCP routing policies, e.g. run the following command on the command-line:
udm policies/dhcp_routing list
You should also check that the correct policies are referenced: either use the "UMC Domain" module "Policies" to list all policies of type "Policy: DHCP routing", open each in turn and see the tab "Referencing objects", which containers use them, or run the following command on the command-line:
univention-ldapsearch -LLLo ldif-wrap=no "univentionPolicyReference=*" dn univentionPolicyReference
The DHCP daemon should be restarted automatically via the Univention Directory Listener; you can do that manually on the command line via
service isc-dhcp-server restart
or using the "UMC Systems" module "System services" to restart named service.
If that still does not resolve your problem, edit the file
/etc/dhcp/dhcpd.conf, remove the
ldap-debug-file, restart the daemon and post the content of the file
/var/log/dhcp-ldap-startup.log which should help us pinpoint, if the right policies get applied.
Last question: are you sure you don't have another DHCP service running in your network? Make sure you have all other DHCP services an your routers turned off.