Capybara added a deprecation warning in version 3.35.3 (version from 2019) that shows up if your selector is not of type String or Symbol.
click_link(10) # bad click_link("10") # good
You might encounter this error e.g. in a pagination step or similar where you want to click on numbers. To figure out where this deprecation warning comes from try to run the tests with a step output.
bundle exec parallel_cucumber --test-options "--format=pretty" feature
The deprecation message looks like following:
Locator Integer:2 for selector :link must be an instance of String or Symbol
Locator Integer:3 for selector :link must be an instance of String or Symbol