Reverse DNS lookups returns two container names for a same container ip with only one replica

I’m resolving an ip client container from a proxy container configured with " endpoint_mode dnsrr" and a shared overlay network to get client container name.

Sometimes client container name is resolved with CONTAINER ID+network name and usually is resolved with
CONTAINER NAME+network name.

Example:

dig -x 10.0.23.3 usually is resolved to containerName.networkname but sometimes is resolved to
containerID.networkname

There’s only one replica but each Docker service.

I need to get always full client container name with a reverse DNS lookup and not containerID.

I’m running Docker EE 18.09.5 with UCP 3.1.6 on RHEL 7.6

Thanks.