Bootcamp partitioning error in macOS 10.13

I had the exact same problem with BootCamp Assistant and solved it with deleting local Time Machine snapshots.

Try my solution if you had turned on Time Machine Back Up Automatically.

1. Turn off "Back Up Automatically" in Time Machine.
2. Type in the command in Terminal to check local snapshots.

   tmutil listlocalsnapshots /

3. Delete snapshot one by one by

   tmutil deletelocalsnapshots <snapshot_date>

   (replace <snapshot_date> with the dates shown in the list, e.g. 2018-01-01-231501).
4. Redo step 2 to check if all the snapshots have been deleted.

Then start over in BootCamp.