Fly not deploying .yml file from Elixir/Phoenix project

Hello, I have successfully deployed a starter Elixir/Phoenix app on Fly.io before.

But now that I’ve added some functionality with a navigation.yml file, somehow that file fails to deploy.

Locally everything works as expected but after I do “fly deploy”, I see the following error message in the logs:
** (MatchError) no match of right hand side value: {:error, %YamlElixir.FileNotFoundError{message: “Failed to open file "/app/bin/config/navigation.yml": no such file or directory”}}

I have double checked that config/navigation.yml is committed and pushed to git. First it was in a different location (inside lib/xxx_web/views) and it gave the same issue.

Do I need to make an explicit change somewhere for fly to upload *.yml files? I have tried adding an explicit command COPY config/navigation.yml config/navigation.yml to Dockerfile but that doesn’t seem to make a difference. Here is my Dockerfile (comments removed for brevity):

ARG BUILDER_IMAGE="hexpm/elixir:1.13.3-erlang-24.2.1-debian-bullseye-20210902-slim"
ARG RUNNER_IMAGE="debian:bullseye-20210902-slim"
FROM ${BUILDER_IMAGE} as builder
RUN apt-get update -y && apt-get install -y build-essential git \
    && apt-get clean && rm -f /var/lib/apt/lists/*_*
WORKDIR /app
RUN mix local.hex --force && \
    mix local.rebar --force
ENV MIX_ENV="prod"
COPY mix.exs mix.lock ./
RUN mix deps.get --only $MIX_ENV
RUN mkdir config
COPY config/config.exs config/${MIX_ENV}.exs config/
COPY config/navigation.yml config/navigation.yml
RUN mix deps.compile
COPY priv priv
COPY assets assets
RUN mix assets.deploy
COPY lib lib
RUN mix compile
COPY config/runtime.exs config/
COPY rel rel
RUN mix release
FROM ${RUNNER_IMAGE}
RUN apt-get update -y && apt-get install -y libstdc++6 openssl libncurses5 locales \
  && apt-get clean && rm -f /var/lib/apt/lists/*_*
RUN sed -i '/en_US.UTF-8/s/^# //g' /etc/locale.gen && locale-gen
ENV LANG en_US.UTF-8
ENV LANGUAGE en_US:en
ENV LC_ALL en_US.UTF-8
WORKDIR "/app"
RUN chown nobody /app
# Only copy the final release from the build stage
COPY --from=builder --chown=nobody:root /app/_build/prod/rel/<appname> ./
USER nobody
CMD ["/app/bin/server"]
# Appended by flyctl
ENV ECTO_IPV6 true
ENV ERL_AFLAGS "-proto_dist inet6_tcp"