Gitlab runner using wrong docker image to build container

Question

I installed gitlab-ci-multi-runner on my virtual machine.
During the build process, I provide a docker container with all the dependencies. But when I run it, the runner uses a different (wrong) docker image for his build container.
Messages look like this:

Working with gitlab-ci-multi-runner 9.2.1 (f0xxxx4)
on runnerVM (f5xxxxf0)
Using the Docker artist with docker.com/xxx/xxx/docker-build:stable image ...
Using the sha256 docker image: fe32xxx ... xxxa63c for a predefined container ...
Pulling docker image docker.com/xxx/xxx/docker-build:stable ...
Using docker image docker.com/xxx/xxx/docker-build:stable ID = sha256: 9608xxx ... xxxdf09 for assembly container ...

Can someone tell me why the runner is using a different docker image for the assembly container?
Why doesn’t it accept a predefined container (because that one is correct ...)

Here you can see my gitlab-ci.yml:

image: docker.com/xxx/xxx/docker-build:stable

before_script:
  - echo "Before script"


after_script:
  - echo "After Script"

stages:
  - build
  - test
  - deploy

build_release:
  stage: build
  script:
    - sudo make all BUILD_TYPE=Release
  only:
    - master
  tags:
    - tag1

build_debug:
  stage: build
  script:
    - sudo make all BUILD_TYPE=Debug
  only:
    - develop
    - runner-test
  tags:
    - tag1
    - tag2

Answer 1

.gitlab-ci.yml URL- ; , , group/container, . library/nginx.

, . library/nginx:1.13.9.

. https://docs.gitlab.com/ce/ci/docker/using_docker_images.html

Answer 2

, . gitlab-ci-runner Image gitlab/gitlab-runner-helper, - VM. .

, , , . .

, image .gitlab-ci.yml. ,

$ docker image ls | grep -E '(fe32|9608)'

. .