docker-compose picks the wrong ruby version – Debian

When running docker-compose, it seems to pick the wrong ruby program.
Using rbenv I have installed version 2.6.2
But there is also a version under /usr/bin that is at 2.6.3. I can’t delete that version, also not as sudo.
I have already uninstalled rbenv and re-installed it.

The strange thing is this:

MBP-Andre:biblestudy_platform andreheijstek$ which ruby
/Users/andreheijstek/.rbenv/shims/ruby
MBP-Andre:biblestudy_platform andreheijstek$ whereis ruby
/usr/bin/ruby

When I run docker-compose, it seems to pick the usr/bin/ruby, which is the wrong one!

I’ve tried to take all the advise under rbenv not changing ruby version but nothing helps.
Any ideas?

Maybe some more background to clarify the situation.
I have followed this advise to dockerise my existing rails app.
https://evilmartians.com/chronicles/ruby-on-whales-docker-for-ruby-rails-development

Here, the docker-compose wil create the docker.
My docker-compose.yml

version: '3.4'

x-app: &app
  build:
    context: .
    dockerfile: ./.dockerdev/Dockerfile
    args:
      RUBY_VERSION: '2.6.2'
      PG_MAJOR: '11'
      NODE_MAJOR: '11'
      YARN_VERSION: '1.13.0'
      BUNDLER_VERSION: '2.0.2'
  environment: &env
    NODE_ENV: development
    RAILS_ENV: ${RAILS_ENV:-development}
  image: example-dev:1.0.0
  tmpfs:
    - /tmp

x-backend: &backend
  <<: *app
  stdin_open: true
  tty: true
  volumes:
    - .:/app:cached
    - rails_cache:/app/tmp/cache
    - bundle:/bundle
    - node_modules:/app/node_modules
    - packs:/app/public/packs
    - .dockerdev/.psqlrc:/root/.psqlrc:ro
  environment:
    <<: *env
    REDIS_URL: redis://redis:6379/
    DATABASE_URL: postgres://postgres:postgres@postgres:5432
    BOOTSNAP_CACHE_DIR: /bundle/bootsnap
    WEBPACKER_DEV_SERVER_HOST: webpacker
    WEB_CONCURRENCY: 1
    HISTFILE: /app/log/.bash_history
    PSQL_HISTFILE: /app/log/.psql_history
    EDITOR: vi
  depends_on:
    - postgres
    - redis

services:
  runner:
    <<: *backend
    command: /bin/bash
    ports:
      - '3000:3000'
      - '3002:3002'

  rails:
    <<: *backend
    command: bundle exec rails server -b 0.0.0.0
    ports:
      - '3000:3000'

  sidekiq:
    <<: *backend
    command: bundle exec sidekiq -C config/sidekiq.yml

  postgres:
    image: postgres:11.1
    volumes:
      - .dockerdev/.psqlrc:/root/.psqlrc:ro
      - postgres:/var/lib/postgresql/data
      - ./log:/root/log:cached
    environment:
      PSQL_HISTFILE: /root/log/.psql_history
    ports:
      - 5432

  redis:
    image: redis:3.2-alpine
    volumes:
      - redis:/data
    ports:
      - 6379

  webpacker:
    <<: *app
    command: ./bin/webpack-dev-server
    ports:
      - '3035:3035'
    volumes:
      - .:/app:cached
      - bundle:/bundle
      - node_modules:/app/node_modules
      - packs:/app/public/packs
    environment:
      <<: *env
      WEBPACKER_DEV_SERVER_HOST: 0.0.0.0

volumes:
  postgres:
  redis:
  bundle:
  node_modules:
  rails_cache:
  packs:

And my Dockerfile

# Taken from: https://evilmartians.com/chronicles/ruby-on-whales-docker-for-ruby-rails-development

ARG RUBY_VERSION
FROM ruby:$RUBY_VERSION

RUN echo RUBY_VERSION

ARG PG_MAJOR
ARG NODE_MAJOR
ARG BUNDLER_VERSION
ARG YARN_VERSION

# Add PostgreSQL to sources list
RUN curl -sSL https://www.postgresql.org/media/keys/ACCC4CF8.asc | apt-key add - 
  && echo 'deb http://apt.postgresql.org/pub/repos/apt/ stretch-pgdg main' $PG_MAJOR > /etc/apt/sources.list.d/pgdg.list

# Add NodeJS to sources list
RUN curl -sL https://deb.nodesource.com/setup_$NODE_MAJOR.x | bash -

# Add Yarn to the sources list
RUN curl -sS https://dl.yarnpkg.com/debian/pubkey.gpg | apt-key add - 
  && echo 'deb http://dl.yarnpkg.com/debian/ stable main' > /etc/apt/sources.list.d/yarn.list

# Install dependencies
COPY .dockerdev/Aptfile /tmp/Aptfile
RUN apt-get update -qq && DEBIAN_FRONTEND=noninteractive apt-get -yq dist-upgrade && 
  DEBIAN_FRONTEND=noninteractive apt-get install -yq --no-install-recommends 
    build-essential 
    postgresql-client-$PG_MAJOR 
    nodejs 
    yarn=$YARN_VERSION-1 
    $(cat /tmp/Aptfile | xargs) && 
    apt-get clean && 
    rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/* && 
    truncate -s 0 /var/log/*log

# Configure bundler and PATH
ENV LANG=C.UTF-8 
  GEM_HOME=/bundle 
  BUNDLE_JOBS=4 
  BUNDLE_RETRY=3
ENV BUNDLE_PATH $GEM_HOME
ENV BUNDLE_APP_CONFIG=$BUNDLE_PATH 
  BUNDLE_BIN=$BUNDLE_PATH/bin
ENV PATH /app/bin:$BUNDLE_BIN:$PATH

# Upgrade RubyGems and install required Bundler version
RUN gem update --system && 
    gem install bundler:$BUNDLER_VERSION

# Create a directory for the app code
RUN mkdir -p /app

WORKDIR /app

When I try to create everything, this happens:

MBP-Andre:biblestudy_platform andreheijstek$ docker-compose up rails
biblestudy_platform_postgres_1 is up-to-date
biblestudy_platform_redis_1 is up-to-date
Starting biblestudy_platform_rails_1 ... done
Attaching to biblestudy_platform_rails_1
rails_1      | Your Ruby version is 2.6.3, but your Gemfile specified 2.6.2
biblestudy_platform_rails_1 exited with code 18