I would like to share an interesting topic which was discussed on the TechNet thread.
The CCMExec.exe takes the ownership and remove all the permissions of the BDP package folder while downloading the package. In normal scenario, CCMExec.exe should reassign package ownership and NTFS permission back after the completion of the download. If the package download is not completed then the package folder on BDP won’t get it’s permission back.
The problem described in the above thread is that the download never gets completed. So the package folder permission is broken.
More details please go through the TechNet thread.