How can I create InternetGatewayDevice.WANDevice.2 when InternetGatewayDevice.WANDevice.1.WANConnectionDevice.3 already exists? When I try to create it, InternetGatewayDevice.WANDevice.4 is created instead. I should not delete InternetGatewayDevice.WANDevice.1.WANConnectionDevice.3, as deleting it will disconnect my network.
Adding an instance doesn’t delete an instance. If one is being deleted, then you either have a provision script which is deleting the instance, or your CPE is deleting the instance.
Instance IDs are not guaranteed, the spec leaves numbering up to manufacturers.