Hypervisor VM fails to back up with warning: not present in any index - Disk '...' was captured by RCT but is not present in the backup checkpoint

Symptoms

• The log displays warnings indicating that specific data chunks are missing from the backup index:

  CONFIG_TEXT: SaveChangedBlocks: Depending on packed <chunk>: <blob> not present in any index (skipping).

• The log displays Hyper-V Resilient Change Tracking (RCT) discrepancies:

  CONFIG_TEXT: Disk '...' was captured by RCT but is not present in the backup checkpoint (skipping).

Cause

A bug in Comet with ID COMET-60193 caused the index to be incomplete and not include some directory tree data from the last backup. 

The bug has been fixed in version 26.8.4 and will be fixed in version 26.10.0.

Resolution

Upgrade the backup agent to 26.8.4.

If the upgarde is not possible for some reason, the missing parts of the index can be reuploaded by disabling Changed Block Tracking for one backup run.

• On Hyper-V and VMware, set the backup type to "Latest VM state (Standard)".

• On Proxmox, set the backup type to "Full"

  After a successful backup in Standard mode, switch back to Changed Block Tracking mode. 

  Monitor the logs in case of further warnings.