Rules with "not" patterns are sometimes fired incorrectly even though there are facts which must not exist.

Issue

When executing a rule with one or more not patterns, the rule is sometimes fired unexpectedly. For example, when I execute a rule (*1) containing a not pattern like (*1-1) with a java code (*2) inserting some facts which must not exist and modifying some properties of one of the facts, the rule (*1) is sometimes fired unexpectedly like (*3-1).

(*1) DRL Rules

dialect "mvel"

rule "cond_1d_01"
    salience 3
    when
        Cheese( $type : type )
        not ( Person( likes == $type, salary == null ) )        // <---------- (*1-1)
    then
        System.out.println("***** Rule \"cond_1d_01\" FIRED!");
end

rule "cond_1d_02"
    salience 2
    when
        Cheese( $type : type )
        $person : Person( likes == $type, name == "George" )
    then
        modify($person) {
            age = 40
        }
        System.out.println("***** Rule \"cond_1d_02\": " + $person);
end

rule "cond_1d_03"
    salience 1
    when
        Cheese( $type : type )
        $person : Person( likes == $type, name == "George" )
    then
        modify($person) {
            salary = new BigDecimal(1000)
        }
        System.out.println("***** Rule \"cond_1d_03\": " + $person);
end

(*2) Java code

Cheese cheese = new Cheese("cheddar");
Person p1 = new Person("John");
p1.setId(1);
p1.setLikes("cheddar");
p1.setSalary(null);
Person p2 = new Person("Paul");
p2.setId(2);
p2.setLikes("cheddar");
p2.setSalary(null);
Person p3 = new Person("George");
p3.setId(3);
p3.setLikes("cheddar");
p3.setSalary(null);

kSession.insert(cheese);
kSession.insert(p1);
kSession.insert(p2);
kSession.insert(p3);

kSession.fireAllRules();

(*3) The result of rule execution

***** Rule "cond_1d_02": com.example.reproducer.Person[id='3', name='George', age='0', likes='cheddar', salary='null']
***** Rule "cond_1d_03": com.example.reproducer.Person[id='3', name='George', age='40', likes='cheddar', salary='null']
***** Rule "cond_1d_01" FIRED!    <---------- (*3-1)