The service that hit it was Sagemaker Notebooks, or specifically underlying EC2 instance (which you normally don't see as customer, afaik) - it failed trying to

The service that hit it was Sagemaker Notebooks, or specifically underlying EC2 instance (which you normally don't see as customer, afaik) - it failed trying to attach a network interface to the instance, because of IAM failure mentioning something rhyming with blown stack (been over a year since, so I don't recall details)