On Yosemite 10.10 Onyx returns the following error:
Error: -69845: File system verify or repair failed Underlying error: 8: POSIX reports: Exec format error The disk needs to be repaired.
I tried repairing the disk in recovery mode but the disk utility returns a message that everything is fine, however, the after running Onyx the second time the error persists.
On a related matter, the option to repair permissions is not available in the Disk Utility.