Source has a call to 'OrderChanges' commented out, which means you have probably run into this type of problem before.

If a changeset contains a 'rename' and an 'add', and they aren't executed in the right order, the conversion will fail.

1.  rename a.jpg to b.jpg
2.  add a.jpg

If it is executed as #1, #2, it's fine.  If it is executed as #2, #1, it will fail.

Similar issues exist for deletes and renames, or deletes and adds, etc.