error 1 again, but on diff

NBU 7.6.0.4

SQL Server 2008 R2, Windows Server 2008 R2

the original post was here https://www-secure.symantec.com/connect/forums/error-1-sql-backup

and also found the solution there. but that was for a full backup.

the same error happens now with the differential backup:

12/06/2015 09:09:06 - Info dbclient (pid=10260) INF - Created VDI object for SQL Server instance <ACMEdb>. Connection timeout is <600> seconds.
12/06/2015 09:19:06 - Info dbclient (pid=10260) ERR - Error in GetConfiguration: 0x80770003.
12/06/2015 09:19:07 - Info dbclient (pid=10260)     CONTINUATION: - The api was waiting and the timeout interval had elapsed.
12/06/2015 09:19:10 - Info dbclient (pid=10260) INF - OPERATION #2 of batch C:\Program Files\VERITAS\NetBackup\dbext\Mssql\acmedbDiffBackup.bch FAILED with STATUS 1 (0 is normal). Elapsed time = 606(606) seconds.

of course, i could always increase the VDI timeout of the client but i feel that's only a workaround.

i also thought that i should move my backup window because on the above link posted, the full backup happened at 1pm to 3pm, but now this differential backup happened. and my differential backup occurs every 4 hours.

is there from NBU side something to fix this permanently?