Credential test fails BE 2012

Hi,

i need your helping solving problems regarding BE2012.

I've read a lot of articles but not helped solving my problems.

I'm using BE 2012, Windows Server 2008 an Exchange 2010.

My first problem is that the credential test failes on Microsoft Information Store. Mailbox databases and PF database. I've check all security groups and access rights. All are ok. I've restart the services all ok. The backup doesn't failes.

Sinds a couple of days my incremental backup of exchange turns in to a full backup what causes my Qnap runs out of disk space. A normal job should be around 25Gb for a incremental and 1,3Tb for a full backup. Now the incremental is 1,3Tb.

I've checked some settings in the job but can't find anything.

I've also a SQL backup job. The credentail test on this also failes but the backup itself is ok.

Please help.