Checking maintenance plan history would help.

select * from msdb.dbo.sysmaintplan_log

select * from msdb.dbo.sysmaintplan_logDetail

The databases selected for backup (in SSIS package) and the current databases in the server may not be...

It is looking like memory page out. Have you changed sql server service account recently? and not changed the same for "Lock pages in memory"? Have a look at it.

If...