+++ This bug was initially created as a clone of Bug #1318052 +++

Description of problem:

For some scenario activation-group is not working properly.
It seems related with Not Nodes.

I am attaching a simple reproducer where two rules in the same activation-group are fired where only one is expected.

Version-Release number of selected component (if applicable):
6.2.1

How reproducible:
Always

Steps to Reproduce:
1. run the attached maven project

Actual results:
Two rules are fired

Expected results:
Only one is expected