Please can someone provide some light on why I am getting the following errors:

We have a local, dev, test and a live instance. 
We can courier from local, to dev, to test to live. 
We can also courier from live to test to dev. 
But when we courier from dev to local we get the following error:

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error:Umbraco.Courier.Core.Exceptions.RetrieveException: Error retrieving item [5d3fd50c-087c-4903-b82b-90944c4dc1b8] from provider [e0472594-e73b-11df-9492-0800200c9a66]. ---> System.NullReferenceException: Object reference not set to an instance of an object. at Umbraco.Courier.Persistence.V6.NHibernate.Persisters.ContentPropertyDataItem.RetrieveItem[T](ItemIdentifier itemId) in c:\Program Files (x86)\teamcity\buildAgent\work\650bafc4b83aa858\Core\Umbraco.Courier.Persistence.V6.NHibernate\Persisters\ContentPropertyData.cs:line 169 at Umbraco.Courier.Core.ItemCrudProvider.RetrieveItem[T](ItemIdentifier itemId) --- End of inner exception stack trace --- at Umbraco.Courier.Core.ItemCrudProvider.RetrieveItem[T](ItemIdentifier itemId) at Umbraco.Courier.ItemProviders.PropertyItemProvider.HandlePack(ItemIdentifier id) at Umbraco.Courier.Core.ItemProvider.Package(ItemIdentifier id) at Umbraco.Courier.RepositoryProviders.Local.Package(ItemIdentifier itemId) at Umbraco.Courier.RepositoryProviders.Local.Hash(ItemIdentifier itemId) at Umbraco.Courier.Core.Packaging.RevisionPackaging.CompareAndStoreItem(Item item, ItemProvider provider, QueuedItemIdentifier itemInQueue) at Umbraco.Courier.Core.Packaging.RevisionPackaging.PackageBatch() at Umbraco.Courier.Core.Packaging.RevisionPackaging.Package() at Umbraco.Courier.Core.TaskManager.manageTask(IRevisionTask value) 23/04/2014 11:43:41 
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error:Umbraco.Courier.Core.Exceptions.PackageException: Unable to load item with id '1153' from provider 'Media' ---> Umbraco.Courier.Core.Exceptions.RetrieveException: Error retrieving item [1153] from provider [d8e6ad87-e73a-11df-9492-0800200c9a66]. ---> System.ArgumentOutOfRangeException: Length cannot be less than zero. Parameter name: length at System.String.InternalSubStringWithChecks(Int32 startIndex, Int32 length, Boolean fAlwaysCopy) at Umbraco.Courier.Persistence.V6.NHibernate.Helpers.MediaHelper.GetFromFileName(String filePath, ISession session) in c:\Program Files (x86)\teamcity\buildAgent\work\650bafc4b83aa858\Core\Umbraco.Courier.Persistence.V6.NHibernate\Helpers\MediaHelper.cs:line 18 at Umbraco.Courier.Persistence.V6.NHibernate.Persisters.MediaItem.RetrieveItem[T](ItemIdentifier itemId) in c:\Program Files (x86)\teamcity\buildAgent\work\650bafc4b83aa858\Core\Umbraco.Courier.Persistence.V6.NHibernate\Persisters\Media.cs:line 77 at Umbraco.Courier.Core.ItemCrudProvider.RetrieveItem[T](ItemIdentifier itemId) --- End of inner exception stack trace --- at Umbraco.Courier.Core.ItemCrudProvider.RetrieveItem[T](ItemIdentifier itemId) at Umbraco.Courier.ItemProviders.MediaItemProvider.HandlePack(ItemIdentifier id) at Umbraco.Courier.Core.ItemProvider.Package(ItemIdentifier id) at Umbraco.Courier.RepositoryProviders.Local.Package(ItemIdentifier itemId) at Umbraco.Courier.Core.Packaging.RevisionPackaging.PackageItem(ItemIdentifier itemId, ItemProvider provider, QueuedItemIdentifier itemInQueue) --- End of inner exception stack trace --- at Umbraco.Courier.Core.Packaging.RevisionPackaging.PackageItem(ItemIdentifier itemId, ItemProvider provider, QueuedItemIdentifier itemInQueue) at Umbraco.Courier.Core.Packaging.RevisionPackaging.PackageBatch() at Umbraco.Courier.Core.Packaging.RevisionPackaging.PackageBatch() at Umbraco.Courier.Core.Packaging.RevisionPackaging.PackageBatch() at Umbraco.Courier.Core.Packaging.RevisionPackaging.PackageBatch() at Umbraco.Courier.Core.Packaging.RevisionPackaging.PackageBatch() at Umbraco.Courier.Core.Packaging.RevisionPackaging.Package() at Umbraco.Courier.Core.TaskManager.manageTask(IRevisionTask value) 23/04/2014 11:44:52 
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The deployment from dev to local use to work fine.

We are also experiencing issues with courier not keeping the folder structure with media files.

Our test server is where our content editors enter all content and media. When you courier from test to dev there is no structure to the media. The media is stored as one massive list.

Thanks