Cant deploy images with WDS: PXE-E16: No offer received

I am currently playing around with a WDS lab environment on a virtual 2012 R2 server, which is patched to the latest available update-level. This server is running the DHCP server role and has two NICs configured. One NIC is bound to a private vSwitch and the other to an external vSwitch (so I can get updates from the internet)

The WDS service itself is configured to respond to any PXE requests (without requiring approval). Within the "Advanced" tab the radio button "Authorize this Windows Deployment Services server in DHCP" is activated. I have added a plain vanilla 2012 R2 install image including the corresponding boot image. Also the DHCP server option 060 PXEClient is set to the value PXEClient (this hasn't been set manually by me).

However my WDS target, which is a generation 2 Hyper-V VM itself (and connected to the same private vSwitch as the WDS server), does not pull the image. This is what the boot process says:

PXE Network Boot using IPv4
....
   Station IP address is 192.168.10.13

   PXE-E16: No offer received.
Boot Failed. EFI Network.
Boot Failed. EFI SCSI Device.
No Operating System was Loaded. Press a key to retry the boot sequence...

I am puzzled. As you can see the PXE client receives an IP address from the DHCP, but somehow can't pull the boot.wim image. The same happens when booting from a generation 1 VM that has a legacy NIC. I have tried enabling and disabling "Secure boot" within the WDS target VM configuration, also changing the VMs MAC address didn't make a change.

What am I doing wrong here?

[addendum-0]

Enabling debug logging under Eventvwr -> Microsoft -> Windows -> Deployment-Services-Diagnostics - Debug isn't revealing anything, only informational messages. Also nothing suspicious in the DHCP-server log.

Is there a way I can completly reset all configurations made within WDS? Deinstalling seems to leave traces somewhere in the registry, which means reinstalling is no option here.

Removing the vNIC which is attached to the external vSwitch didnt make a change as well.

[addendum-1]

I tried moving the DHCP server role onto another server. But now I cant supply the PXE option to server. Its not visible from the options menu. Again Microsofts documentation is a PITA… How do I set the option?

[addendum-2]

I still can't get it working. Here is my wireshark trace. 192.168.10.2 is my 2012 R2 DHCP server without any option set as it is on the same broadcast domain/subnet as the WDS server. 192.168.10.1 is my WDS machine.

[addendum-3]

To be more specific, this is only related to generation 2 virtual machines. Generation 1 VMs can be PXE-booted via legacy vNIC without any issues.