Hi Torsten,
Here's something you can try using.
Dell's BMC tool has IPMITOOL to reset the drac card without flashing any of the existing configurations.
It is some sort a cold reboot of the DRAC card.
The place to download the ipmi tool :
downloads-us.dell.com/.../OM-BMC-Dell-Web-WIN-7.1.0-5304_A00.exe
The command to run: ipmitool mc reset cold
Let me know if the update is successful.