Unable to provision using archivematica playbook with vars-singlenode-qa.yml (on Windows)

I've tried to provision a few times now using vars-singlenode-qa.yml instead of vars-singlenode-1.6.yml, and I keep getting the same error.

TASK [artefactual.archivematica-src : Checkout archivematica-storage-service code] ***
fatal: [am-local]: FAILED! => {"changed": false, "cmd": "/usr/bin/git checkout --track -b qa/0.x origin/qa/0.x", "failed": true, "msg": "Failed to checkout qa/0.x", "rc": 1, "stderr": "error: Your local changes to the following files would be overwritten by checkout:\n\t
storage_service/static/js/vendor/base64.js\nPlease, commit your changes or stash them before you can switch branches.\nAborting\n", "stderr_lines": ["error: Your local changes to the following files would be overwritten by checkout:", "\tstorage_service/static/js/vendor/
base64.js", "Please, commit your changes or stash them before you can switch branches.", "Aborting"], "stdout": "", "stdout_lines": []}
to retry, use: --limit @/vagrant/singlenode.retry

When I look at src/archivematica-storage-service, I see that branch stable/0.10.x is checked out even though archivematica_src_ss_version is set to "qa/0.x".

roles/artefactual.archivematica-src/tasks/ss-main.yml looks good. The version corresponds to the yml file and force is set to "yes".

Investigating...

Start with roles/artefactual.archivematica-src/tasks/ss-main.yml and vars-singlenode-qa.yml, then reproduce the provisioning failure on Windows. Check why the storage-service checkout remains on stable/0.10.x and leaves storage_service/static/js/vendor/base64.js modified; done means the qa/0.x checkout completes successfully.

Written by the indexing model from the issue text.