MDK 5 Network: DHCP offer ignored when relay agent ip is missing

After a customer of us switched to a different device as DHCP-relay-agent, our devices no longer receive an address via DHCP. The only difference we can find when tracing the DHCP-offer is that the relay agent ip-address is empty:

All other devices in the network still receive their addresses via DHCP. Is their a setting in MDK-Network to ignore a missing relay agent ip address or another way to still receive an ip address via DHCP?