AWS CodeBuild taking FOREVER on transfer to S3 step

I built a CodeBuild project for a fairly simple build pipeline. I am building a NodeJS project. My buildspec is pretty simple:

version: 0.2
env:
  variables:
    ENVIRNOMENT: "AWSDEV"
phases:
  pre_build:
    commands:
      - npm install
  build:
    commands:
      - npm run -s build
artifacts:
  files:
    - src/dist/**/*
    - node_modules/**/*
  discard-paths: no

The npm run build step simply uses Babel to transpile the code into the src/dist directory. I'm running a build and it's been 37 minutes and it's still building, on the step UPLOAD_ARTIFACTS. I can see the artifacts being added to the S3 bucket so it's presumably actually still doing stuff.

Is there anything I can do to improve this build process? This should be a short, 5 minute at most task I would think. Am I doing something wrong by uploading node_modules to the S3 bucket?

What is the best configuration for a Node project?