GitLab cache not found in second job

According to the documentation, "Subsequent jobs in the same pipeline can use the cache, if the dependencies are identical." I have the following in my gitlab-ci.yml file:

slowcompile:
  stage: build
  needs: [verdate]
  dependencies: [verdate]
  cache:
    key: "$EXTERNALS_VERSION"
    paths: [ externals/*, externals_st/*, fast*/*, slow*/* ]
    policy: pull
  script:
    - ./buildstep.pl slowcompile
  artifacts:
    when: always
    paths:
      - log*/*
      - slow*/*

slow:
  stage: build
  needs: [verdate, slowcompile]
  dependencies: [verdate]
  cache:
    key: "$EXTERNALS_VERSION"
    paths: [ externals/*, externals_st/*, fast*/*, slow*/* ]
    policy: pull
  script:
    - measure ./buildstep.pl slowfilein
  artifacts:
    when: always
    paths:
      - log*/*
      - slow*/gs/*
      - slow*/GemStone64Bit*-slow.zip

The first job shows the following output when it runs:

Restoring cache                               02:31
Checking cache for externals-2025-09-09-non_protected...
No URL provided, cache will not be downloaded from shared cache server. Instead a local version of cache will be extracted. 
Successfully extracted cache

The second job shows the following output when it runs:

Restoring cache                               00:01
Checking cache for externals-2025-09-09-non_protected...
No URL provided, cache will not be downloaded from shared cache server. Instead a local version of cache will be extracted. 
WARNING: Cache file does not exist                 
Failed to extract cache

Since they both have the same cache definition including a "policy: pull", and since nothing else is running, I don't understand why the cache fails to exist for the second job. When the pipeline is rerun, the first job finds the cache (without recreating it), so I know it is still present.