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Request you to please provide a screen shot by clicking on view details tab on Backup Iteam page for a data source which you have deleted from MABS Server. Also, provide a screen shot from MABS ->Protection Tab to be sure that it is deleted.
Sometime, there is a sync issue between MABS Server and Portal due to which the backup items still show on Portal. If you could provide me the details maybe I could help you to get to a resolution for this issue.