Ruby bundle caching fails to restore gems from cache

Build Environment
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1

Bundle installs over the web from rubygems.org every time, never the local circleci cache.
$ bundle install --gemfile=./my_rail_app_dir/Gemfile

The cache for python pip dependencies works fine.

As you can see in logs below, CircleCi saves the bundle cache, /home/ubuntu/.bundle, , and but fails to load it with the other programminglanguage caches when I click ‘Rebuild’.

Machine:

Restore cache:
restoring cache v5/os:linux/my_username/my_app/dependency/pusher/292/c_EG0w1b4D8BgWhixvdL2Q__.tar.gz
restoring home/ubuntu/virtualenvs, home/ubuntu/.m2, home/ubuntu/.ivy2, home/ubuntu/.go_workspace, home/ubuntu/.gradle

Save cache
Creating dependency cache from the following paths:
  ✗ /home/ubuntu/.bundle
  ✗ /home/ubuntu/.cache/bower
  ✓ /home/ubuntu/.go_workspace
  ✓ /home/ubuntu/.gradle
  ✓ /home/ubuntu/.ivy2
  ✓ /home/ubuntu/.m2
  ✗ /home/ubuntu/my_app/vendor/bundle
  ✓ /home/ubuntu/virtualenvs
Creating source cache from the following paths:
✓ /home/ubuntu/my_app/.git
2

Could you please share your circle.yml?