Having some issues migrating a public folder.

Migrating a large public folder has 400+ subfolders and is nearly 70GB.  So far 45GB has been migrated but is failing with the error below.  

Cannot lock the storage. Try again later.(The remote server returned an error: (409) Conflict.)

Repeats this 3 times then pauses and retries until it fails completely.  

Anyone seen this before?