GitLab CI fails after checkout

I am trying to setup the GilLab CI to do CD for an iOS Application.

I setup Fastlane and the GitLab runner on a MacMini but when I execute the pipeline It always fails without even starting the real job itself. The error I get is the following:

Running with gitlab-runner 11.11.2 (ac2a293c)
  on MacMini 4o3qWqUf
Using Shell executor...
Running on newminus.home...
Reinitialized existing Git repository in /Users/[----]/winews/winews-ios/.git/
ERROR: Job failed: exit status 1

This is the .gitlab-ci.yml I have

  - build
  - checks
  - testflight

  - gem install bundler
  - bundle install
  stage: build
  script: fastlane build --env ci

  stage: checks
  script: fastlane check --env ci
#  only:
#    - merge_requests
      - fastlane/artifacts

  stage: testflight
  script: fastlane release
    - web

Any ideas?

The only environment variable I have is the DEVELOPER_DIR that points to the Xcode to use.

If it helps in the e-mail of the failing pipeline I have some additional informations:

Running with gitlab-runner 11.11.2 (ac2a293c)
  on MacMini 4o3qWqUf
section_start:1560524788:prepare_executorUsing Shell executor...
section_end:1560524788:prepare_executorsection_start:1560524788:prepare_scriptRunning on newminus.home...
section_end:1560524788:prepare_scriptsection_start:1560524788:get_sourcesReinitialized existing Git repository in /Users/user/builds/4o3qWqUf/0/winews-ios/.git/
section_end:1560524789:get_sourcessection_start:1560524789:upload_artifacts_on_failuresection_end:1560524789:upload_artifacts_on_failureERROR: Job failed: exit status 1

Here the versions of the tools:

 GitLab 11.11.3 (e3eeb779d72)

GitLab Shell 9.1.0

GitLab Workhorse v8.7.0

GitLab API v4

Ruby 2.5.3p105

Rails 5.1.7

PostgreSQL 9.6.11

GitlabRunner 11.11.2