The reason this occurs is because the user running Template Builder does not have read permissions to the folder that this TBB is in. The TBB runs in Template Builder, but none of the metadata about the TBB is available due to the permissions setting.
Also note, when publishing items that rely on the template where some TBBs don't have read permissions, the template will publish without error, but the TBBs without permissions within will not do anything. So your published output will not be correct.