See this project, which is based on the standard Sample.drl of the Drools Eclipse plugin: https://github.com/DuncanDoyle/DroolsConditionalNamedConsequenceIssue

The 'src/main/resources/rules/Sample.drl' contains a rule which uses a 'Conditional Named Consequence' construct. When clicking the Rete Tree tab in the DRL editor I receive this error:

Rete Tree Build Error!

Reason:
org.drools.core.RuntimeDroolsException:
java.lang.reflect.InvocationTargetException : [Rete(0)]

And the Rete Tree is not displayed.