EC2 UDP Network Loadbalancer does not forward client IP

Hi
Issue:

using a UDP network loadbalancer with eks terminated at a mqttsn server does not show up the client ip but remoteaddr is within the ip range of the subnets.

Expected Behavior:
The client IP as described in https://aws.amazon.com/de/about-aws/whats-new/2019/06/network-load-balancer-now-supports-udp-protocol/
is preserved.

Any pointers how to fix / hanldethis issue?
Thanks