Ember build issue: "Cannot use the decorators and decorators-legacy plugin together"

I have recently encountered an issue with building my ember project with bitbucket pipelines:

+ ember build --environment="production"
Could not start watchman
Visit https://ember-cli.com/user-guide/#watchman for more info.
Building
Environment: production
cleaning up
cleaning up...
Build Error (broccoli-persistent-filter:Babel > [Babel: ember-data]) in ember-data/adapters/json-api.js
Cannot use the decorators and decorators-legacy plugin together

I am currently using ember-cli version 3.8.1.

The issue occurs with all build environments, not just production. What baffles me is that no new npm package or ember addon was added between last successful build and the ones that have been failing since - and now if I re-run the successful build, that will also fail.

I have gone back in the commit history to a commit that worked, then fast-forward into the present step-by-step - always deleting the node_modules and reinstalling the packages. It always works locally, but it will always fail when the pipeline is run.

I have also tried updating my docker image.

I have already gone through and tried the solutions listed here - but it seems like they have already been addressed in version 3.8.1.

Also, if it is any help, this is my bitbucket-pipelines.yml:

pipelines:
  branches:
    master:
      - step:
         name: Building Ember Project
         script:
          - npm install
          - npm install firebase-tools
          - ember build --environment="production"
      - step:
         trigger: manual
         deployment: production
         name: Deploy to Production
         script:
          - firebase use prod
          - firebase deploy --non-interactive --token ${FIREBASE_TOKEN}

Thank you all in advance!