VM becomes unresponsive with "Another task is already in progress" error during or after VM backup

Products

• VMware vSphere ESXi
• VMware vCenter Server

Issue/Introduction

• During snapshot consolidation or deletion, a VM may become unresponsive to all inputs.
• Attempts to shut down the VM or create/remove snapshots fail with the error message:
  

  Another Task is already in progress

• This blocks further administrative tasks and affects normal VM operations

Environment

• VMware vCenter Server 7.x
• VMware vCenter Server 8.x

Cause

During scheduled backups using a 3rd party solution, the backup solutions create a snapshot on the VM but may fail to delete it post-completion. Over a period of time, this snapshot will grow significantly and could cause task process delays due to the size of the snapshot disk. A stale snapshot chain or an underlying task lock could cause the VM become unresponsive, and common actions like VM power operations or snapshot deletion will time out or fail.

Resolution

1. Refer to the Broadcom Knowledge article Powering off an unresponsive virtual machine on an ESXi host to identify and cancel the stuck task. This helps release any backend lock on the VM.

2. Restart the management agents Restarting Management Agents in ESXi on the ESXi host. This can help reset host-side services and clear stale states.

3. If the above methods do not help, migrate or shut down all VMs on the affected ESXi host. Then, log in to the host via iLO/DRAC and perform a COLD Boot to reset the host state fully to get rid of the stale vm process.

4. Try excluding the VM from the backup schedule to see if the lock is released, then attempt to remove the snapshot.
   
   
5. If the issue still persists, restoring the VM from a recent backup or cloning the VM is recommended.

For best practices regarding VMware snapshot usage and cleanup, refer Broadcom Knowledge article: Best practices for using VMware snapshots in the vSphere environment