Only one sub path of traefik rule works

Traefik Traefik v1
1

I have two labels like this

    labels:
      traefik.iipax.frontend.rule: "Host:main-one.test.localhost"
      traefik.iipax.port: "4567"
      traefik.mgmt.frontend.rule: "Host:main-two.test.localhost"
      traefik.mgmt.port: "7654"

Then I have one docker container behind main-one.test.localhost with two http-reachable web applications verified up and running (application-one and application-two). Looking in the traefik dashboard I can see main-one.test.localhost is mapped to :. When trying to click a link like

main-one.test.localhost:<frontend-port>/application-one

I can reach application-one, but when clicking a link like

main-one.test.localhost:<frontend-port>/application-two

I get "Internal Server Error". When using the backend ip like specified in the dashboard

<main-one-ip>:<backend-port>/application-two

directly I can though see that I can reach application-two. What is the problem here?