ruby on rails - Capistrano all of sudden stopped working -

i deploying rails 4.1 code using capistron 2.

everything working fine did changes in schedule.rb file whenever i.e.

set :output, {:error => 'error.log', :standard => 'cron.log'} 

to

set :output, {:error => 'log/error.log', :standard => 'log/cron.log'} 

and deployed code , worked fine first time.

now when deployed again, firstly faced error during deployment.

bundler: command not found: whenever 

i installed whenever gem separately on production:-

gem install whenever -v 0.9.4 

now on deploy again, still broken , error is:-

executing "cp -- /home/myusername/project/production/shared/assets/manifest-74e7866cd14bb57f565f7e816b8116fd.json /home/myusername/project/production/releases/database.yml/assets_manifest.json  failed access ‘/home/myusername/project/production/releases/database.yml/assets_manifest.json  [whenever:update_crontab] rolling 

the 1 thing confused why moving manifest file releases/database.yml/assets_manifest.json directory should release number.