https://www.theregister.co.uk/2017/09/20/macos_high_sierra_more_like_cry_sierra_for_some_beta_testers/

Apple's next version of the macOS, High Sierra, aka 10.13, is due for general release next week, and users running the beta have already noticed a pair of issues that could cloud the rollout.

The Cupertino phone flinger says that the Apple File System (APFS), a technology unveiled last year for the Mac, is going to cause some problems with Apple Fusion drives that will require anyone using the beta to revert their disks back to the old format.