Traefik 502 Bad Gateway with WSS on AWS ECS Fargate

Hi,

I'm trying to run a secured websocket service, as well as a HTTPS service in an AWS Fargate task.
I use traefik with an ECS provider to do the routing inside the task.
My HTTPS service is working great but the WSS isn't : I get a 502 Bad Gateway error

Here is the log that I get :

level=debug msg="'502 Bad Gateway' caused by: EOF"

Here is my (simplified) JSON file that I use to deploy my task definition :

Container 1 is the one with WSS,
Container 2 is the one with HTTPS,

{
  "containerDefinitions": [
    {
      "portMappings": [
        {
          "hostPort": 443,
          "protocol": "tcp",
          "containerPort": 443
        },
        {
          "hostPort": 8080,
          "protocol": "tcp",
          "containerPort": 8080
        }
      ],
      "image": "traefik",
      "name": "Traefik",
      "command": [
        "--api.dashboard=true",
        "--api.insecure=true",
        "--log.level=DEBUG",
        "--providers.ecs=true",
        "--providers.ecs.exposedbydefault=false",
        "--providers.ecs.autoDiscoverClusters=false",
        "--providers.ecs.clusters=ClusterName",
        "--entrypoints.websecure.address=:443",
        "--serversTransport.insecureSkipVerify=true"
      ]
    },
    {
      "portMappings": [
        {
          "hostPort": 1234,
          "protocol": "tcp",
          "containerPort": 1234
        }
      ],
      "image": "xxx",
      "name": "Container1",
      "dockerLabels": {
        "traefik.enable": "true",
        "traefik.port": "1234",
        "traefik.http.routers.container1-router.tls": "true",
        "traefik.http.routers.container1-router.rule": "PathPrefix(`/container1`)",
        "traefik.http.routers.container1-router.entrypoints": "websecure",
        "traefik.http.middlewares.container1-strip.stripprefix.prefixes": "/container1",
        "traefik.http.middlewares.container1-strip.stripprefix.forceSlash": "false",
        "traefik.http.routers.container1-router.middlewares": "container1-strip"
      }
    },
    {
      "portMappings": [
        {
          "hostPort": 5000,
          "protocol": "tcp",
          "containerPort": 5000
        }
      ],
      "image": "xxx",
      "name": "Container2",
      "dockerLabels": {
        "traefik.enable": "true",
        "traefik.port": "5000",
        "traefik.http.routers.container2-router.tls": "true",
        "traefik.http.routers.container2-router.rule": "PathPrefix(`/container2`)",
        "traefik.http.routers.container2-router.entrypoints": "websecure",
        "traefik.http.middlewares.container2-strip.stripprefix.prefixes": "/container2",
        "traefik.http.middlewares.container2-strip.stripprefix.forceSlash": "false",
        "traefik.http.routers.container2-router.middlewares": "container2-strip"
      }
    }
  ]
}

The traefik dashboard displays my router just fine so I can't figure what might be the issue ?
Thanks,

Any info in the debug log?