VDP keep perform full backup of some VMs

Hi,

I am using VDP5.5.6 version.

I find that the VDP always perform full backup on some of the VMs especial VMs with large disk size. I tried to backup the VM again just after it completed but the task is still (F).

Everytime, the full backup take over 20hr and I really don't know why there are only Full backup.

Anyone has the same problem?

Karl