APFS and disk changes
The developer of Carbon Copy Cloner (CCC) found a serious problem with APFS-formatted sparse disk images. This kind of image is designed to expand as data is added, up to the limit of the volume on which it’s stored. However, APFS-formatted sparse disk images fail to track free space accurately, and so allow storage operations to continue even if there isn’t room on the underlying volume.
A file might seem to copy to an image, but remounting the image will reveal the file is corrupted or missing. CCC has removed support for this type of image. But, if you create sparse disk images using Disk Utility — say, to keep an encrypted and password-protected copy of your tax return in the cloud — stick with Mac OS Extended format.
A specific kind of disk image, when formatted as APFS and getting full, runs the risk of losing data.