{
  "$schema": "http://schema.management.azure.com/schemas/2015-01-01/deploymentParameters.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "vmSku": {
      "value": "Standard_A1"
    },
    "ubuntuOSVersion": {
      "value": "16.04.0-LTS"
    },
    "vmssName": {
      "value": "GEN-UNIQUE-32"
    },
    "instanceCount": {
      "value": 5
    },
    "adminUsername": {
      "value": "ubuntu"
    },
    "adminPassword": {
      "value": "GEN-PASSWORD"
    }
  }
}

{
  "$schema": "http://schema.management.azure.com/schemas/2015-01-01/deploymentParameters.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "vmSku": {
      "value": "Standard_A1"
    },
    "ubuntuOSVersion": {
      "value": "16.04-LTS"
    },
    "vmssName": {
      "value": "GEN-UNIQUE-32"
    },
    "instanceCount": {
      "value": 5
    },
    "adminUsername": {
      "value": "ubuntu"
    },
    "adminPassword": {
      "value": "GEN-PASSWORD"
    }
  }
}

Change Ubuntu 16.04.0-LTS to 16.04-LTS
Change Ubuntu 16.04.0-LTS to 16.04-LTS