Resource tries to pull image with incorrect digest

We're seeing a repeat of issue #33 on Concourse CI 6.5.1. We have two tasks in our pipeline that use the same Docker image (same tag). One of them is pulling the correct SHA and the other is failing because it's trying to pull a completely different non-existent SHA. The resource_type definition for the task looks like:

- name: node
  source:
    ca_certs:
    - cert: |
        ((shared.ca-cert))
      domain: '*.our-domain.local'
    repository: harbor.our-domain.local/tools/node
    tag: 13.14.0-ubuntu
  type: docker-image

The first stage succeeds:

Pulling harbor.our-domain.local/tools/node@sha256:5d8f1447da011d2a9215ee312f61ebf49dc00f1173ff40c0e6ba1b9a95819002...
sha256:5d8f1447da011d2a9215ee312f61ebf49dc00f1173ff40c0e6ba1b9a95819002: Pulling from tools/node
3ff22d22a855: Pulling fs layer
...
2d4b3890a2e6: Pull complete
Digest: sha256:5d8f1447da011d2a9215ee312f61ebf49dc00f1173ff40c0e6ba1b9a95819002
Status: Downloaded newer image for harbor.our-domain.local/tools/node@sha256:5d8f1447da011d2a9215ee312f61ebf49dc00f1173ff40c0e6ba1b9a95819002
harbor.our-domain.local/tools/node@sha256:5d8f1447da011d2a9215ee312f61ebf49dc00f1173ff40c0e6ba1b9a95819002

The second fails as follows:

waiting for docker to come up...
Pulling harbor.our-domain.local/tools/node@sha256:6298b1ee476e73f76c06ff99105eedb1290355f09a367ab06d5fd5d334ad8b6a...
Error response from daemon: manifest for harbor.our-domain.local/tools/node@sha256:6298b1ee476e73f76c06ff99105eedb1290355f09a367ab06d5fd5d334ad8b6a not found: manifest unknown: manifest unknown

Pulling harbor.our-domain.local/tools/node@sha256:6298b1ee476e73f76c06ff99105eedb1290355f09a367ab06d5fd5d334ad8b6a (attempt 2 of 3)...
Error response from daemon: manifest for harbor.our-domain.local/tools/node@sha256:6298b1ee476e73f76c06ff99105eedb1290355f09a367ab06d5fd5d334ad8b6a not found: manifest unknown: manifest unknown

Pulling harbor.our-domain.local/tools/node@sha256:6298b1ee476e73f76c06ff99105eedb1290355f09a367ab06d5fd5d334ad8b6a (attempt 3 of 3)...
Error response from daemon: manifest for harbor.our-domain.local/tools/node@sha256:6298b1ee476e73f76c06ff99105eedb1290355f09a367ab06d5fd5d334ad8b6a not found: manifest unknown: manifest unknown

No source file or test entry point is identified. Start by reproducing the two tasks that use the same Harbor image tag on Concourse CI 6.5.1, then trace how each task resolves the image digest; done means both tasks request the valid digest consistently and have regression coverage.