PermissionError: Permission denied: '/taiga/static/admin'

[nidupb]

This error shows up on synology when starting taiga docker :
PermissionError: [Errno 13] Permission denied: '/taiga/static/admin'

That is my docker-compose file :

version: "2"

services:
  postgresql:
    image: sameersbn/postgresql:10-2
    restart: always
    environment:
      - DB_NAME=taigadb
      - DB_USER=taiga
      - DB_PASS=myPWD
    volumes:
      - /volume1/docker/postgres:/var/lib/postgresql:Z
    ports:
      - "5432"

  taiga:
    image: nemonik/taiga:latest
    restart: always
    environment:
      - DEBUG=True
      - HOST=127.0.0.1
      - PORT=80
      - SCHEME=http
      - DB_HOST=postgresql
      - DB_PORT=5432
      - DB_NAME=taigadb
      - DB_USER=taiga
      - DB_PASSWORD=myPWD
    #      - LDAP_SERVER=ldap://FDQN
    #      - LDAP_PORT=389
    #      - LDAP_BIND_DN=uid=SERVICE ACCOUNT DN
    #      - LDAP_BIND_PASSWORD=PASSWORD
    #      - LDAP_SEARCH_BASE=BASE DN FOR USERS
    #      - LDAP_SEARCH_FILTER_ADDITIONAL=(uid=*)
    #      - LDAP_EMAIL_ATTRIBUTE=mail
    #      - LDAP_FULL_NAME_ATTRIBUTE=cn
    #      - LDAP_USERNAME_ATTRIBUTE=uid
    volumes:
      - /volume1/docker/Taiga/media:/taiga/media:Z
      - /volume1/docker/Taiga/static:/taiga/static:Z
    ports:
      - "8280:8080"
    depends_on:
      - postgresql

I don't have any issue with the PostgresSQL container who can write in the /volume1/docker/postgres folder. My experience with docker is limited, could it be related to missing APP_UID and APP_GID environment variable ?