How to get good debugging messages with ruby/setup-ruby@v1 in github CI

Have an old legacy Ruby/Rails project using Ruby 2.3.x that I'm trying to setup in CI.

I'm doing something like the following in the ci.yml that runs the CI steps in github.

    runs_on: ubuntu-latest
    steps:
      - uses: ruby/setup-ruby@v1
        with:
          ruby-version: 2.3
          bundler-cache: true
          cache-version: 1

The various Ruby versions (2.3, 2.4, etc) won't install and I get cryptic messages like

Error: The process '/opt/hostedtoolcache/Ruby/2.3.8/x64/bin/bundle' failed with exit code 5

What does this mean and/or how do I get better error messages to point me to the actual issue?