Ran into an issue where I didn't find anything on the community hence this post. Working on an instance that had a lot of pre-existing CI's in their CMDB and I was trying to setup their CMDB Health Dashboard. Specifically, I was trying to resolve an issue with the Duplicate KPI rendering an Incomplete Score.

When I looked in the logs, I found the following error:

CMDBHealth : DUPLICATE error : java.lang.NumberFormatException: For input string: "null"

at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)

After some trial and error, what I learned was that there were a number of CI's that had a Discovery Source = '-- None --'

Changing to value to anything else got me past the error and allowed the Duplicate KPI to compute correctly.

Hope that helps...