Selenium webdriver error with Caybara in CI system

Recently I´m experimenting a strange issue in my Capybara ruby tests in CI system. Every test launched 600 times in a row, is being failed around 30 times (570 succed, 30 failed) The errors are mainly of 2 types:

-Net::ReadTimeout (Net::ReadTimeout)

-unable to bind to locking port 9514 within 45 seconds (Selenium::WebDriver::Error::WebDriverError)

All the tests run against Chrome. Always in the first step (login step), and only in CI system, running locally is always fine. There are some problem with my CI machine? Some ruby gem update? Chomedriver update?

Thanks!!!!