Federation doesnt work

Hey, are there any issues with the federation between Docker installations and Release installations?
I have two instances, one is 3.0.3(Release) and one is Docker(2.1.0) both run on the same Server. One is the Main Instance domain.tld and the other one is a topic specific instance sub.domain.tld
The Request from the 2.1.0 to the 3.0.3 goes trough but the other way around i dont get a request.

Was an issue with the nginx config file for the docker installation. Can i find somewhere an known good/working nginx conf file for the Docker installation?