VMSS instances unexpectedly stopped with no caller-bearing Activity Log event

https://learn.microsoft.com/en-us/answers/questions/5975731/vmss-instances-unexpectedly-stopped-with-no-caller?page=1&orderby=helpful
Asked this question but need additional investigation from azure side.
The cluster autoscaler hypothesis has been ruled out: autoscaling is disabled for both pools, both use  scaleDownMode: Delete ,  autoScalerProfile  is null, and no AKS/agent-pool scaling operation exists in the incident window. The portal prevents filing a restored Severity B/C incident under our Internal support plan. Please escalate this thread privately to Azure Compute/AKS Support for backend correlation. I cannot open the case via the Azure portal.