Weird (websocket) disconnecting issue (Proxmox behind Traefik)

Traefik Traefik v2
1

Hello there!

I have set up a Traefik instance for internal use in our company. I've already put several services behind it and that all went smoothly.

Until I tried to put the Proxmox WebUI behind the proxy. The entire UI seems to be working as intended except for the VNC part. It starts up normally and seems to be running fine up until about 30 seconds where the entire VNC window just freezes up.

I've checked the network tab under my browser devtools and it seems that the websocket it uses for the inputs / video data just doesn't get any data back anymore. The browser still sends out data but it never receives anything anymore.

I've put the relevant pieces of the traefik config below:
proxmox-app.yaml

http:
  routers:
    pve-app-redirect:
      entryPoints:
        - "http"
      rule: "Host(`pve-app.int.domain.tld`)"
      middlewares:
        - secured
      service: pve-app

    pve-app:
      entryPoints:
        - "https"
      rule: "Host(`pve-app.int.domain.tld`)"
      middlewares:
        - secured
      tls: {}
      service: pve-app

  services:
    pve-app:
      loadBalancer:
        servers:
          - url: "https://10.11.1.1:8006"
          - url: "https://10.11.1.2:8006"
          - url: "https://10.11.1.3:8006"
        passHostHeader: true
        healthCheck:
          path: /
          interval: "5s"
          timeout: "3s"
        sticky:
         cookie: {}

middlewares.yaml

http:
  middlewares:
    redirect:
      redirectScheme:
        scheme: https
        permanent: true

    default-headers:
      headers:
        frameDeny: true
        sslRedirect: true
        browserXssFilter: true
        contentTypeNosniff: true
        forceSTSHeader: true
        stsIncludeSubdomains: true
        stsPreload: true
        stsSeconds: 15552000
        customFrameOptionsValue: SAMEORIGIN
        customRequestHeaders:
          X-Forwarded-Proto: https


    default-whitelist:
      ipWhiteList:
        sourceRange:
        - "10.0.0.0/8"
        - "192.168.0.0/16"
        - "172.16.0.0/12"

    public:
      chain:
        middlewares:
        - redirect
        - default-headers

    secured:
      chain:
        middlewares:
        - redirect
        - default-whitelist
        - default-headers

If there's any more information needed to diagnose this issue please let me know!