one vps, multiple docker images?

Im currently running WPT agents in docker containers on VPSes at a remote location, but am only able to start one docker container per VPS. Here is the command I used to create the original container:

docker run -d --restart always -e SERVER_URL="" -e LOCATION="Europe" -e NAME="Docker Test" --cap-add=NET_ADMIN wptagent

This is working great, and is persistent on reboot. I have three VPSes and one container each, so three test nodes. But, if I start a second container on each server with the same command, the /install/ info page on the master server ( still only lists the original number of VPSes I have set up (3) as listening for the Europe location. I tried redirecting a different port to 80 by adding:

-p 4000:80

… to the container create command, but this doesn’t affect the /install/ count of listeners. I even altered the NAME variable, to no effect.

It seems such a waste to have these relatively beefy VPSes (4 core 4G RAM) set up and only have one worker per VPS; I feel they should be able to handle at least three or four apiece. How can I start several wptagent docker images on the same server and have them be unique listeners?

i also attempted to assign a specific ip address to each docker container, passing ports 80 and 443 though

docker run -d --restart always -p -p ...

… and a different ip for the second container. this also has had no effect on the install page, are there ports other than 80 and 443 i should be passing? does the install count by respondent ips as i assumed for this test, or by hostnames, or by something else?