When a model is created as a different modeltype than what is configured in the database, CA Spectrum will generate a "modeltype mismatch" alarm indicating the model does not match the type that is configured in the database. If a scheduled Discovery with the "Discover Connections During Scheduled Discovery" option is selected contains that model, CA Spectrum will destroy the model and recreate it as the modeltype configured in the SSdb.
This generally happens with non certified models. For example, if you have a Cisco device that is not certified and you have modeled it as an SwCiscoIOS modeltype, when the discovery runs it will destroy and recreate the model as either a GnSNMPDev or a GnCiscoDev.
Before the scheduled discovery runs, add/change the modeltype setting for the System Object ID that your device has by using the "Device Certification..." option in OneClick. You can do this by going to "Tools->Utilities->Device Certification...". In the Device Certification gui, find the System Object ID for your device and edit it. Change the modeltype to the modeltype that you need. For instance, if the Device Certification window shows GnSNMPDev, yet it should be a SwCiscoIOS, change the modeltype to SwCiscoIOS. The modeltype mismatch alarm will clear and when the scheduled discovery runs it will not destroy/recreate the model.