BucketManager.MoveItemIntoBucket results in IOException: The directory is not empty. (sometimes)

[JaapioNL]

Hi I am not sure if to put this in Unicorn or Rainbow.

When I call BucketManager.MoveItemIntoBucket to move a freshly created item I, sometimes, get an IOException: The directory is not empty. The reason I say sometimes is that sometimes it runs hundres of times and things are just fine but sometimes I get this exception:

Rainbow.Storage.SfsDeleteException: 'Error deleting SFS directory D:\xyzxyzxyz\Repo\sitecore\src\Sitecore.Data\Unicorn\xyz-xyz-xyz\master_xyz\65d63815-2f19-f285-9a10-2183297215ef'

IOException: The directory is not empty.

This exception was originally thrown at this call stack:
System.IO.__Error.WinIOError(int, string)
System.IO.Directory.DeleteHelper(string, string, bool, bool, ref Microsoft.Win32.Win32Native.WIN32_FIND_DATA)
System.IO.Directory.Delete(string, string, bool, bool)
Rainbow.Storage.SerializationFileSystemTree.RemoveWithoutChildren.AnonymousMethod__2()
Rainbow.ActionRetryer.Perform(System.Action)
Rainbow.Storage.SerializationFileSystemTree.RemoveWithoutChildren(Rainbow.Model.IItemMetadata)

Sitecore version: 9.0.1
Unicorn version: 4.0.4 (with transparent sync enabled)

Also something weird, normally items are located in:
D:\xyzxyzxyz\Repo\sitecore\src\Sitecore.Data\Unicorn\xyz-xyz-xyz\master_xyz\xyzxyzxyz xyz xyz\Content\Products

But sometimes it ends in the folder above.