ERROR: Job failed: exit status 1 on multi-runner

Hello,
I use an multi-runner under debian, without docker, for an grails project. Sometimes the runner failed with:

Running with gitlab-runner 10.1.0 (c1ecf97f)
  on multi-runner (0904d94c)
Using Shell executor...
Running on repo...
Fetching changes...
warning: failed to remove .gradle/
Removing .gradle/3.5
Removing .gradle/daemon
Removing .gradle/buildOutputCleanup
Removing .gradle/wrapper
Removing .gradle/caches
Removing .gradle/native
Removing build/
Removing logs/
ERROR: Job failed: exit status 1

or:

Running with gitlab-runner 10.1.0 (c1ecf97f)
  on multi-runner (0904d94c)
Using Shell executor...
Running on repo...
Fetching changes...
warning: failed to remove .gradle/
Removing .gradle/3.5
Removing .gradle/daemon
Removing .gradle/buildOutputCleanup
Removing .gradle/wrapper
Removing .gradle/caches
Removing .gradle/native
Removing build/
ERROR: Job failed: exit status 1

If I retry the job runs fine.
Where I can find more log output or debug informations?

This is the beginning of .gitlab-ci.yml

stages:
  - build
  - test
  - deploy

before_script:
  - echo `pwd` # debug
  - echo "$CI_BUILD_NAME, $CI_BUILD_REF_NAME $CI_BUILD_STAGE" # debug
  - export GRADLE_USER_HOME=`pwd`/.gradle

cache:
  paths:
    - .gradle/wrapper
    - .gradle/caches

Thank you for helping