--footer not showing when using wkhtmltopdf within a docker container

I am trying to deploy a flask (python) app that uses wkhtmltopdf.

Everything works perfectly when it is run in a debug environment, however when I run it using docker, it stops showing footers and headers.

I suspect it has something to do with the way Docker installs wkhtmltopdf.

Here is my Dockerfile

# set base image (host OS)
FROM python:3.9
RUN apt-get update && \
    apt-get install -y locales && \
    sed -i -e 's/# es_ES.UTF-8 UTF-8/es_ES.UTF-8 UTF-8/' /etc/locale.gen && \
    dpkg-reconfigure --frontend=noninteractive locales
ENV LC_TIME es_ES.UTF-8

# I BELIEVE I AM MISSING SOMETHING HERE
RUN apt-get install wkhtmltopdf -y

# set the working directory in the container
WORKDIR /app
ENV PYTHONPATH "${PYTHONPATH}:/app/src"

# copy the dependencies file to the working directory
COPY requirements.txt .

# install dependencies
RUN pip install -r requirements.txt

# copy the content of the local src directory to the working directory
COPY . .

# command to run on container start
CMD [ "gunicorn", "src.wsgi:app","--bind","0.0.0.0:5000" ]

Here are the relevante python requirements in case they might be useful.

PyPDF2==1.26.0
pdfkit==0.6.1

Any help will be much appreciated. Thanks!

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