Backups take longer because the VM has a snapshot.
Backups are taking longer because ABM and CBT are not working.
Cause of this is that VM has a snapshot.
There will be the following log entries in the backup log:
Skipping active map of vix:r:esvc.pce.era.cz:902:[LUN1] VM/VM-000002.vmdk because the virtual machine has a snapshot.
Skipping change block because virtual machine has a snapshot.
Consolidate or delete the snapshot(s) of the VM in Snapshot Manager pror to running the backup job containing said VM.