Internal Server Error (Rails Mina+passenger+ngnix ) rack-preloader.rb not found

Problem : when you  tail -200f /opt/nginx/logs/error.log 
Error msg:ruby: No such file or directory -- /home/ubuntu/.rvm/gems/ruby-2.3.1@<gemset-name>/gems/passenger-5.1.2/src/helper-scripts/rack-preloader.rb

Solution:
Login to production/staging server and got to app folder (verify gemset selected if using rvm)
just manually installed the same passenger version as

gem i passenger -v='5.1.2'