We are using a custom Docker image in Bitbucket pipeline, this image has a default user setup. When the Cache files are generated during the installation process in the Pipeline build, those files are getting generated using this default user as the owner.

During the build teardown process cache files are compressed using the same default user and all the files are uploaded for the cache.

However, when those caches are extracted during the build setup in the subsequent builds, those files are always extracted using the Root user (not the default user). Since Root user doesn't have access to those files, the files are not extracted and not available subsequently during the build process. Hence, few files are not being extracted and we observe discrepancy in the number of files uploaded and extracted in the cache.

Workaround:

• Use an image that has root as the default user in the build image.
• Specify the root as run time user using the following syntax for the image 

  image:
    name: image_name
    run-as-user: 0