I would suggest setting the below discovery server loglevel and size.
Discovery cfg/logs and other sql outputs are missing covering period of robot rediscovery
1. Set the discovery_server at log level 5, increase log size to 10MB, and increase number of file to retain.
a. To increase the log size edit the X..\Nimsoft\probes\service\discovery_server\log4j.xml
change the follow values as shown below:
<param name="MaxFileSize" value="10242880"/>
<param name="MaxBackupIndex" value="15"/>
b. To increase the log level use raw configure for the Discovery_server, set setup loglevel to 5
2. Deactivate the Discovery_server and delete all discovery_server logs
3. Activate the Discovery_server
Go into USM and delete the system in question. Make sure NOT to check the boxes to remove data or exlude from discovery.
Restart the robots and then monitor the discovery_Server logs you will see where they are first added back and then correlated and the reason for it in the discovery_server logs.
details on this
Device Correlation Configuration - CA Unified Infrastructure Management Probes - CA Technologies Documentation
make sure to set loglevel back to 0 once done.