Can't click the Rails app for Heroku

Suddenly, we cannot push our Rails application to Heroku-, not in the same way as in the intermediate or production environment, as well as the new application that we just set up for testing. This application works on Heroku for 9 months with a few taps per week without any problems, but as of yesterday, after some harmless changes to the model file, we get the following error:

-----> Ruby app detected
-----> Compiling Ruby/Rails
-----> Using Ruby version: ruby-2.0.0
-----> Installing dependencies using 1.5.2
       New app detected loading default bundler cache
       Running: bundle install --without development:test --path vendor/bundle --binstubs vendor/bundle/bin -j4 --deployment sh: Syntax error: "(" unexpected
       Bundler Output:  !  !     Failed to install gems via Bundler.  !

 !     Push rejected, failed to compile Ruby app

UPDATE:
What crazy thing is that we just returned everything until the last commit that was successfully deployed to Heroku, and it still fails. In other words, the same code was deployed perfectly several days ago, and now we get this error.

??