I recently suffered through this. Could you try to bring the scope outside of properties please?

{
  "type": "Microsoft.Storage/storageAccounts/providers/roleAssignments",
  "name": "[concat(variables('storageAccountName'),'/Microsoft.Authorization/',guid(subscription().subscriptionId))]",
  "apiVersion": "2019-04-01-preview",
  "dependsOn": [
    "[resourceId('Microsoft.Storage/storageAccounts/blobServices', variables('storageAccountName'), 'default')]",
    "[resourceId('Microsoft.Storage/storageAccounts', variables('storageAccountName'))]"
  ],
  "scope": "[resourceId('Microsoft.Storage/storageAccounts', variables('storageAccountName'))]"
  "properties": {
    "roleDefinitionId": "[concat(resourceGroup().id, '/providers/Microsoft.Authorization/roleDefinitions/17d1049b-9a84-46fb-8f53-869881c3d3ab')]",
    "principalId": "[parameters('principalId')]"
  }
}