Code changes updated for python files but not html

I am running three containers in development, 1) Python with a Django app, 2) a PostgreSQL database, and 3) Redis. The app runs smoothly,

A volume is configured for container #1 (“app” below), and updates to code in Python files do update automatically and fairly quickly with a message like /path/to/ changed, reloading. But updates to html files do not. This makes things extremely difficult for tweaking JavaScript actions and appearance obviously – I have to restart the container for each change to take effect.
I can’t find any reference to a similar problem in my web searches. StackExchange posts (and Docker documentation) indicate all that’s needed is a volume mapping, which I have. Maybe I’m overlooking something obvious?

The docker-compose file includes a volume mapping and that service looks like this

    platform: linux/amd64
    container_name: 'myapp'
      context: .
        - DEV=true
      - "8001:8000"
      - ./app:/app
    command: >
      sh -c "python wait_for_db &&
             python migrate &&
             python runserver &&
             celery -A whg worker -l INFO &&
             alias ll='ls -lha'"
      - DB_HOST=db
      - DB_NAME=devdb
      - DB_USER=devuser
      - DB_PASS=changeme
      - DEBUG=1
      - db