It may be useful to delete the Time Machine local snapshots before verifying the structure of the file system to speed up the operation.
You can use the Maintenance pane to delete the existing Time Machine local snapshots. However, for security reasons, a new local snapshot is automatically created.
You can use the Utilities > Time Machine pane to show the Time Machine local snapshots, to create one, and to delete them all.
Important: Deleting the Time Machine local snapshots can take a very long time to complete. Wait for the task to finish.
Note: Older snapshots are automatically deleted by Time Machine after a period of time or when additional space is needed. If you choose to delete your snapshots and your Time Machine backup is unavailable or corrupted, then you will not be able to recover recent changes to your files.