FabricVmCreationError

I used a custom template to create a deployment, which succeeded yesterday.
The same template today fails with the following message:

{
"code": "DeploymentFailed",
"message": "At least one resource deployment operation failed. Please list deployment operations for details. Please see https://aka.ms/arm-debug for usage details.",
"details": [
{
"code": "Conflict",
"message": "{\r\n \"status\": \"Failed\",\r\n \"error\": {\r\n \"code\": \"ResourceDeploymentFailure\",\r\n \"message\": \"The resource operation completed with terminal provisioning state 'Failed'.\",\r\n \"details\": [\r\n {\r\n \"code\": \"FabricVmCreationError\",\r\n \"message\": \"Failed to create VM 'NetScaler-VPX-Express' \"\r\n }\r\n ]\r\n }\r\n}"
}
]
}

Have any idea what may be the cause of this instability in deployments?