WRF24WB0MA no response to DHCP MAC broadcast

Hi all,

 it's the first time, I am using the TCP/IP Stack with the WRF24WB0MA 
WiFi module on a Explorer 16 starter kit. Almost everything seems to 
work fine in the infrastructure network, except DHCP client. Wireshark 
shows, that the DHCP discovery is sent and a DHCP offer comes back from 
the router - with correct data to the broadcast MAC FF:FF:FF:FF:FF:FF 
with my MAC address in the DHCP data field. But the offer is simply 
ignored. For debug reasons I display all received MAC packages on UART 
inside the StackTask() routine. Works on DNS requests and pings, but not 
when a DHCP offer comes.   After 3 days, I have no more ideas, where to 
look. Does anybody has an idea, how to handle the broadcasts?   

TCP/IP Stack version is 5.42.04  

Thank you and best regards 
Michael