Drone Server respond Invalid Response

I’m trying to set up drone manage server for bitbucket server. I launched the server on EC2 and create application link for it. I got below error when I access to drone server.


This is my docker-compose.yml

version: "3"
services:
  drone-server:
    image: drone/drone:1.6
    restart: always
    ports:
      - 80:80
      - 443:443
    volumes:
      - /var/lib/drone:/data
      - /etc/bitbucket/key.pem:/etc/bitbucket/key.pem
    environment:
      - DRONE_AGENTS_ENABLED=true
      - DRONE_GIT_PASSWORD=MTUxNzk5N...
      - DRONE_GIT_USERNAME=<account name>
      - DRONE_GIT_ALWAYS_AUTH=false
      - DRONE_STASH_SERVER=https://bitbucket.example.com
      - DRONE_STASH_CONSUMER_KEY=OauthKey
      - DRONE_STASH_CONSUMER_SECRET=od6ec55d...
      - DRONE_STASH_PRIVATE_KEY=/etc/bitbucket/key.pem
      - DRONE_STASH_DEBUG=true
      - DRONE_SERVER_HOST=drone.example.com
      - DRONE_SERVER_PROTO=https
      - DRONE_RPC_SECRET=od6ec55d...
      - DRONE_TLS_AUTOCERT=true
      - DRONE_LOGS_COLOR=true
      - DRONE_LOGS_DEBUG=true
      - DRONE_LOGS_TRACE=true
      - DRONE_LOGS_PRETTY=true

Why this error occur and where can I find the error logs? I can not find detail logs in drone’s stacktrace.

Bitbucket Server: v6.5.0

Here is Bitbucket Server Application Link Settings.