Exchange Dag - Incremental backup fails with Highest log index from previous backup: 004A8829, lowest current log index: 004B1DF6, terminating backup

When choosing the "incremental option" in backing up Exchange 2010 DAG, the backup fails with the following Error message.  Do you know why this is occurring?  When I switch the backup backup back to Full backup, the backup seem to run without errors, but it runs slowly( I presume its because its backup up everything).

2016-12-31 12:56:58 avexvss Error <0000>: Log file gap detected in USAWDB024 between current backup and last backup. (Log #2)

2016-12-31 12:56:58 avexvss Error <0000>: Highest log index from previous backup: 004A8829, lowest current log index: 004B1DF6, terminating backup. (Log #2)

2016-12-31 12:56:58 avexvss Error <19214>: Error validating backup log file history: 0x80004005 (Log #2)

2016-12-31 12:56:50 avexvss Info <19007>: Adding writer Microsoft Exchange Replica Writer  GUID: {76fe1ac4-15f7-4bcd-987e-8e1acb462fb7}  Instance: {7a30ff15-f44a-4b65-90fc-fab8114fffc0}

2016-12-31 12:56:50 avexvss Info <19007>: Adding writer Microsoft Exchange Writer  GUID: {76fe1ac4-15f7-4bcd-987e-8e1acb462fb7}  Instance: {ddcfa3fb-82b7-4f6f-bc5c-ab55bd2719eb}

2016-12-31 12:56:51 avexvss Info <16242>: Current log files for database USAWDB033 are 00384118 through 00387FCE.

2016-12-31 12:56:51 avexvss Info <16243>: Checking for log file continuity with previous backup.

2016-12-31 12:56:52 avexvss Info <16242>: Current log files for database USAWDB031 are 0002D416 through 000335BF.

2016-12-31 12:56:52 avexvss Info <16243>: Checking for log file continuity with previous backup.

2016-12-31 12:56:54 avexvss Info <16242>: Current log files for database USAWDB023 are 0025A365 through 00262710.

2016-12-31 12:56:54 avexvss Info <16243>: Checking for log file continuity with previous backup.

2016-12-31 12:56:58 avexvss Info <16242>: Current log files for database USAWDB029 are 003F3ABB through 003FDE09.

2016-12-31 12:56:58 avexvss Info <16243>: Checking for log file continuity with previous backup.

2016-12-31 12:56:58 avexvss Info <16242>: Current log files for database USAWDB024 are 004B1DF6 through 004B22D8.

2016-12-31 12:56:58 avexvss Info <16243>: Checking for log file continuity with previous backup.

2016-12-31 12:56:58 avexvss Error <0000>: Log file gap detected in USAWDB024 between current backup and last backup.

2016-12-31 12:56:58 avexvss Error <0000>: Highest log index from previous backup: 004A8829, lowest current log index: 004B1DF6, terminating backup.

2016-12-31 12:56:58 avexvss Error <19214>: Error validating backup log file history: 0x80004005

2016-12-31 12:56:58 avexvss Info <9772>: Starting graceful (staged) termination, Exiting main body (wrap-up stage)

2016-12-31 12:56:58 avexvss Info <7753>: Exit main body...

2016-12-31 12:56:58 avexvss Info <13180>: Final summary...

2016-12-31 12:56:58 avexvss Info <13181>: snapview_wid: Exchange DAG-1483217751837#0

2016-12-31 12:56:58 avexvss Info <7271>: Final summary generated subwork 0, cancelled/aborted 0, snapview 0, exitcode 536870919

2016-12-31 12:57:03 avexvss Info <12951>: Plug-in avexvss returning with exitcode 536870919