Impossible to upload documents on folder of document libraries with custom path - microsoft-graph-api

Question

We are connecting to a Sharepoint site having multiple document libraries. Some of the document libraries are created with a custom path. To do this we use the "url" property as described in the documentation (https://msdn.microsoft.com/EN-US/library/office/microsoft.sharepoint.client.listcreationinformation_members.aspx).
As a result, the document libraries have following path in our Sharepoint site:
/sites/customers/CUSTOM_PATH/DocLib1/
/sites/customers/CUSTOM_PATH/DocLib2/
/sites/customers/CUSTOM_PATH/DocLib3/
...
Those document libraries also have multiple folders.
When uploading a document, for instance, to the folder ABC of DocLib1, the documents are not uploaded to the ABC folder. Instead, we have new folders "DocLib1/ABC" being created in the document library.
To upload the document via the graph API we use following endpoint:
https://graph.microsoft.com/v1.0/drives/DRIVE_ID/items/ABC_FOLDER_ID:/FILE_NAME:/createUploadSession
Reproduction scenario:
Create a document library DocLib1 using a custom URL path ( see URL property in https://msdn.microsoft.com/EN-US/library/office/microsoft.sharepoint.client.listcreationinformation_members.aspx).
Create a folder ABC in that document library
Upload a document to that folder using https://graph.microsoft.com/v1.0/drives/DRIVE_ID/items/ABC_FOLDER_ID:/FILE_NAME:/createUploadSession
Upload the document to the returned uploadUrl
Expected result: The document is uploaded in the ABC folder of document library DocLib1
Actual result: The document is uploaded in new folders "DocLib1/ABC" created in document library DocLib1
Did you face that issue before ? Are you aware of any workaround to go over it ?
Best regards,
Cyril.