Virtual Machine snapshot stuck in "Source not locked" state and times out with "deadline exceeded"

Issue

• Snapshots timeout, never progress from Source not locked state.

  apiVersion: snapshot.kubevirt.io/v1alpha1
  kind: VirtualMachineSnapshot
  ...
  status:
    conditions:
    - lastProbeTime: null
      lastTransitionTime: "2024-09-18T18:13:48Z"
      reason: Source not locked              <-----------------
      status: "False"
      type: Progressing
    - lastProbeTime: null
      lastTransitionTime: "2024-09-18T18:13:48Z"
      reason: Not ready
      status: "False"
      type: Ready
    - lastProbeTime: null
      lastTransitionTime: "2024-09-18T18:19:17Z"
      reason: snapshot deadline exceeded    <------------
      status: "True"
      type: Failure