Assets only compiled after old releases purged when deploying with Capistrano - ruby-on-rails-4

Question

...I think that's what's happening anyway.
I'm deploying a Rails app to EC2 with Capistrano. The deployment always succeeds, but even if I've just pushed JS/CSS changes to Git, the assets won't compile the first time. When I kept 5 releases, I had to repeat the deployment until all of the old releases were eventually removed. I reduced it to 3, and then to 1. Now, I see a new version of the JS and CSS after 2 consecutive deployments.
In production there are also multiple application.js and application.css files in the shared/public/assets folder including the latest compiled version. Older versions don't seem to get cleaned unless I run rake assets:clobber. rake assets:clean doesn't remove them. I assume it's okay to have more than one version of an asset as long as the manifest points at the right file.
I'd really like assets to precompile when there are new changes. Any help would be appreciated.
Gemfile
gem 'rails', '4.2.3'
gem 'mysql2'
gem 'haml-rails', '~> 0.9'
gem 'sass-rails', '~> 5.0'
gem 'autoprefixer-rails'
gem 'bootstrap-sass', '~> 3.3.5'
gem 'font-awesome-rails'
gem 'uglifier', '>= 1.3.0'
gem 'coffee-rails', '~> 4.1.0'
gem 'therubyracer', platforms: :ruby
gem 'jquery-rails'
gem 'underscore-rails'
gem 'ejs'
gem 'turbolinks'
gem 'jbuilder', '~> 2.0'
gem 'sdoc', '~> 0.4.0', group: :doc
group :development do
gem 'capistrano', '~> 3.4.0'
gem 'capistrano-rails', '~> 1.1'
gem 'capistrano-rbenv', '~> 2.0'
gem 'capistrano-passenger'
end
group :development, :test do
gem 'byebug'
gem 'web-console', '~> 2.0'
gem 'spring'
end
Capfile
require 'capistrano/setup'
require 'capistrano/deploy'
require 'capistrano/rbenv'
require 'capistrano/rails'
require 'capistrano/passenger'
deploy.rb
set :keep_releases, 1
namespace :deploy do
after :restart, :cleanup, :clear_cache do
on roles(:web), in: :groups, limit: 3, wait: 10 do
...
end
end
end
Capistrano Output
INFO [b2b76675] Running RBENV_ROOT=~/.rbenv RBENV_VERSION=2.2.2 ~/.rbenv/bin/rbenv exec bundle exec rake assets:precompile as ec2-user#xx.xxx.xxx.xxx
DEBUG [b2b76675] Command: cd /var/www/my-app/releases/20150918071822 && ( RBENV_ROOT=~/.rbenv RBENV_VERSION=2.2.2 RAILS_ENV=production RBENV_ROOT=~/.rbenv RBENV_VERSION=2.2.2 ~/.rbenv/bin/rbenv exec bundle exec rake assets:precompile )
INFO [b2b76675] Finished in 2.014 seconds with exit status 0 (successful).

Answer 1

Make sure that you are running latest sprockets and sprockets-rails. If you have tmp/cache in linked_dirs, remove it.
If that fixes it and you want the shared cache back, you can try to write a Capistrano task which deletes the contents of tmp/cache/assets at the beginning of deployment.