Capistrano: The deploy has failed with an error: #<Errno::EPROTO: Protocol error @ rb_file_s_stat

Question

I am working to upgrade an app to Rails 4/Ruby 2/Cap 3. I feel as if I am 80% there. When running the following capistrano deploy task:

task :copy_shared_db_config do
  on roles(:app) do 
    execute "mkdir -p #{shared_path}/config"
    example_config_contents = File.read('config/database.example.yml')
    upload!(example_config_contents, "#{shared_path}/config/database.yml", :via => :scp)
  end
end

I receive the following error:

The deploy has failed with an error: #<Errno::EPROTO: Protocol error @ rb_file_s_stat -

The deploy works fine when I am not using this task. The error mystifies me on where to start debugging.

Update:

I am almost positive that the error has to do with my usage of the update! method, which I believe puts this error into the realm of SSHKit.