VM backup failing with "Unable to delete pre-existing snapshots: Another task is already in progress."

VM backup failing for a single VM.
Creating a manual snapshot for the VM also fails with the below error : 

Stale task is shown on the ESXi host for that particular VM.

1) Log into the vcenter and check if there are any old snapshots attached to the VM (if present - delete/consolidate them).
2) Check if there are any snapshots present on the vproxy ( if present - delete/consolidate them).

If no older snapshots seen on the VM or the vproxy perform the below steps to check for active tasks of the VM on the ESXI host:

1) Log into the ESX host at the console or via SSH

2) In order to generate a list of tasks associated to specific virtual machines, you must first get the Vmid of the virtual machine. Run the command:
vim-cmd vmsvc/getallvms
The output is similar to:
Vmid Name File Guest OS Version Annotation
112 VM-1 [Datastore] VM-3/VM-3.vmx winLonghornGuest vmx-04
128 VM-2 [Datastore] VM-3/VM-3.vmx winXPProGuest vmx-04
144 VM-3 [Datastore] VM-3/VM-3.vmx winNetStandardGuest vmx-04

3) Make note of the values under the Vmid column as they are referenced in later steps.

4) When you have the Vmid, you can then get a list of tasks associated with a specific virtual machine. Run the command:
vim-cmd vmsvc/get.tasklist VMID
Where VMIDis the number identified in step 3.
The output is similar to:
(ManagedObjectReference) [
'vim.Task:haTask-112-vim.VirtualMachine.createSnapshot-3887'
]

5) Make note of the task identifier. In the example above, the task identifier is:
haTask-112-vim.VirtualMachine.createSnapshot-3887

6) To get information about the status of a particular task, run the command:
vim-cmd vimsvc/task_info task_identifier
Where task_identifier is the string recorded in step 5.
The output is similar to:
(vim.TaskInfo) {
dynamicType = <unset>,
key = "haTask-112-vim.VirtualMachine.createSnapshot-3887",
task = 'vim.Task:haTask-112-vim.VirtualMachine.createSnapshot-3887',
description = (vmodl.LocalizableMessage) null,
name = "vim.VirtualMachine.createSnapshot",
descriptionId = "VirtualMachine.createSnapshot",
entity = 'vim.VirtualMachine:112',
entityName = "deploy-test",
state = "running",
cancelled = false,
cancelable = false,
error = (vmodl.MethodFault) null,
result = <unset>,
progress = 15,
reason = (vim.TaskReasonUser) {
dynamicType = <unset>,
userName = "root",
},
queueTime = "2012-11-28T01:29:35.233835Z",
startTime = "2012-11-28T01:29:35.234891Z",
completeTime = <unset>,
eventChainId = 2936866,
changeTag = <unset>,
parentTaskKey = <unset>,
rootTaskKey = <unset>,


If any active tasks are present, this needs to be confirmed again by the VMware team and next action to be taken accordingly by VMware support.