DX NetOps

Does anyone have an idea why CA Spectrum (10.2) suddenly stops adding devices to the "Cisco IOS - SSH capable" or "Cisco IOS" device families?

All criteria are met but the server just leaves the device family empty

The device you are referring to is part of the NCM supported device list?

Devices Supported by Network Configuration Manager - CA Spectrum - 10.2 and 10.2.1 - CA Technologies Documentation 

Did you try to reevaluate NCM device faily? Right click the device-->Reconfiguration --> Reevaluate NCM Device Family?

Does it work?

Yes, it is - just a regular Cisco router or switch - previously all went into the correct device family.

All of a sudden, new devices (same model) stop being modeled correctly even after reconfiguration - they stay without a device family

Try comparing the Model Type of the device working and the one which is notworking ? There is a know issue for one specific device in 10.2 take a look at the below

Symptom: Unable to use NCM as Cisco 819 series devices are modeled as GnCiscoDev and the Device Type is Cisco ASR9000LC. 
Resolution: User can perform NCM operations with Cisco 819 series devices modeled as Rtr_Cisco type.
(10.2.0, DE156812, 00345236)