SUMMARY
Sharepoint backups are failing within the application itself and permissions are all confirmed correct
ISSUE
Sharepoint backup failing for error "Object Search_Service_Application_DB_2fc8ab4a68aa40768ed2dbabc7ef5654 failed in event OnBackup"
You will also need to find Event ID 2587 events in Event Viewer with the description:
The following conditions are currently affecting index propagation to this server for search service application 'Search Service Application':
1. Query 0, catalog Main: failing to copy index files from crawl component 0 for 1490 minutes. Access is denied. 0x80070005
2. Query 0 is not being automatically disabled because the minimum number of ready query components per partition is 2.
RESOLUTION
You will need to clear the index and restart the indexing service to remove corrupted indices:
https://social.technet.microsoft.com/Forums/office/en-US/b90263c7-066a-44f7-ac4b-da0d70a72960/query0-server-not-responding-event-id-2587?forum=sharepointadminprevious
CAUSE
Sharepoint Search Service indices are corrupt or the indexing server is not responding