Bombich has a workaround in a beta, but this is BAD.
www.macrumors.com
APFS Bug in macOS 10.15.5 Catalina Impacts the Creation of Bootable Backups
An Apple File System bug has been discovered in macOS 10.15.5 Catalina that can prevent users from making a bootable clone of their system drive, according to the creator of Carbon Copy Cloner. In a blog post on Wednesday, software developer Mike Bombich explained that the CCC team had uncovered...