Docker doesn't find file - docker

Question

I'm working on a project that uses a Docker image for a specific feature, other than that I don't need docker at all so I don't understand much about it. The issue is that Docker doesn't finds a file that is actually in the folder and the build process breaks.
When trying to create the image using docker build -t project/render-worker . the error is this:
Step 18/23 : RUN bin/composer-install && php composer-setup.php --install-dir=/bin && php -r 'unlink("composer-setup.php");' && php /bin/composer.phar global require hirak/prestissimo
---> Running in 695db3bf2f02
/bin/sh: 1: bin/composer-install: not found
The command '/bin/sh -c bin/composer-install && php composer-setup.php --install-dir=/bin && php -r 'unlink("composer-setup.php");' && php /bin/composer.phar global require hirak/prestissimo' returned a non-zero code: 127
As mentioned the file composer-install does exist and this is what's in it:
#!/bin/sh
EXPECTED_SIGNATURE="$(wget -q -O - https://composer.github.io/installer.sig)"
php -r "copy('https://getcomposer.org/installer', 'composer-setup.php');"
ACTUAL_SIGNATURE="$(php -r "echo hash_file('SHA384', 'composer-setup.php');")"
if [ "$EXPECTED_SIGNATURE" != "$ACTUAL_SIGNATURE" ]
then
echo 'ERROR: Invalid installer signature'
rm composer-setup.php
fi
Basically this is to get composer as you can see.
This is the Docker file:
FROM php:7.2-apache
RUN echo 'deb http://ftp.debian.org/debian stretch-backports main' > /etc/apt/sources.list.d/backports.list
RUN apt-get update
RUN apt-get install -y --no-install-recommends \
libpq-dev \
libxml2-dev \
ffmpeg \
imagemagick \
wget \
git \
zlib1g-dev \
libpng-dev \
unzip \
mencoder \
parallel \
ruby-dev
RUN apt-get -t stretch-backports install -y --no-install-recommends \
libav-tools \
&& rm -rf /var/lib/apt/lists/*
RUN docker-php-ext-install \
pcntl \
pdo_pgsql \
pgsql \
soap \
gd \
zip
RUN gem install compass
RUN a2enmod rewrite
ENV APACHE_RUN_USER root
ENV APACHE_RUN_GROUP root
EXPOSE 80
WORKDIR /app
COPY . /app
# Configuring apache to run the symfony app
COPY config/docker/apache.conf /etc/apache2/sites-enabled/000-default.conf
RUN echo "export DATABASE_URL" >> /etc/apache2/envvars \
&& echo ". /etc/environment" >> /etc/apache2/envvars
RUN wget -cqO- https://nodejs.org/dist/v10.15.3/node-v10.15.3-linux-x64.tar.xz | tar -xJ
RUN cp -a node-v10.15.3-linux-x64/bin /usr \
&& cp -a node-v10.15.3-linux-x64/include /usr \
&& cp -a node-v10.15.3-linux-x64/lib /usr \
&& cp -a node-v10.15.3-linux-x64/share /usr/ \
&& rm -rf node-v10.15.3-linux-x64 node-v10.15.3-linux-x64.tar.xz
RUN bin/composer-install \
&& php composer-setup.php --install-dir=/bin \
&& php -r "unlink('composer-setup.php');" \
# Install prestissimo for dramatically faster `composer install`
&& php /bin/composer.phar global require hirak/prestissimo
RUN APP_ENV=prod APP_SECRET= DATABASE_URL= AWS_KEY= AWS_SECRET= AWS_REGION= MEDIA_S3_BUCKET= \
GIPHY_API_KEY= FACEBOOK_APP_ID= FACEBOOK_APP_SECRET= \
GOOGLE_API_KEY= GOOGLE_CLIENT_ID= GOOGLE_CLIENT_SECRET= STRIPE_SECRET_KEY= STRIPE_ENDPOINT_SECRET= \
THEYSAIDSO_API_KEY= REV_CLIENT_API_KEY= REV_USER_API_KEY= REV_API_ENDPOINT= RENDER_QUEUE_URL= \
CLOUDWATCH_LOG_GROUP_NAME= \
php /bin/composer.phar install --no-interaction --no-dev --prefer-dist --optimize-autoloader --no-scripts \
&& php /bin/composer.phar clear-cache
RUN npm install \
&& node_modules/bower/bin/bower install --allow-root \
&& node_modules/grunt/bin/grunt
# Don't allow it to keep logs around; they're emitted on STDOUT and sent to AWS
# CloudWatch from there, so we don't need them on disk filling up the space
RUN mkdir -p var/cache/prod && chmod -R 777 var/cache/prod
RUN mkdir -p var/log && ln -s /dev/null var/log/prod.log \
&& ln -s /dev/null var/log/prod.deprecations.log && chmod -R 777 var/log
CMD ["/usr/bin/env", "bash", "./bin/start_render_worker"]
Like I said, unfortunately I don't have the slightest idea of how docker works and what's going on, just that I need it. I'm running docker in Win10 Pro and to make matters even worst it is actually working for another dev running Win10. We tried a few things but we can't make it work. I tried cloning the repo in other locations with no success at all. Everything before this particular step runs correctly.
[EDIT]
As suggested by the users I ran RUN ls bin/ before the composer install line and this is the result:
Step 18/24 : RUN ls bin/
---> Running in 6cb72090a069
append_captions
capture
composer-install
concat_project_video
console
encode_frames
encode_frames_to_gif
format_video_for_concatenation
generate_meme_bar
image_to_video
install.sh
phpcs
phpunit
process_render_queue
publish_docker_image
run_animation_worker
run_render_worker
run_render_worker_osx
start_render_worker
update
Removing intermediate container 6cb72090a069
As you can see composer-install is there so this is quite baffling.
Also I checked and set the line ending sequence to LF and the result is the same error.
[SECOND EDIT]
I added COPY bin/composer-install /bin
Then RUN ls bin/
And the results are the same. The ls command finds the file but the error persists. Also adding a slash before bin doesn't change anything :(