Task of downloading an artifact in bamboo-specs gives non-informative error

[mgvali]

I'm using Bamboo 8.2.

According to specs manual at https://docs.atlassian.com/bamboo-specs-docs/8.2.0/specs.html?yaml#using-a-shared-artifact-in-another-plan

I'd be able to build an artifact from PROJECTA_PLANA and use it from PROJECTB_PLANB.

Given the publish part shows artifacts actually in Bamboo web ui according to specs -- ie. the scripts artifact is present after build:

version: 2
plan:
  project-key: PROJECTA
  key: PLANA
..

Build:
  artifacts:
   - name: scripts
    required: true
    pattern: '*.sh'
    shared: true 

Trying to download fails with "Bamboo YAML import failed: Document structure is incorrect: Sandbox / tasks / [0]: Unknown task type artifact-download"

version: 2
deployment:
  source-plan: PROJECTB_PLANB
..
Sandbox:
  tasks:
    - artifact-download:
      source-plan: PROJECTA_PLANA

 I've also tried variations according to manual in vain, for example:

version: 2
deployment:
  source-plan: PROJECTB_PLANB
..
Sandbox:
  tasks:
    - artifact-download:
      source-plan: PROJECTA_PLANA
      artifacts:
        - destination: ./scripts
          name: scripts

How would I debug this issue further, please?