Memory leak after retracting fact

Issue

When executing following drl file (Constraint_Error.drl)

package com.sample;

import java.util.Date;
import com.sample.Constraint_Error.Person;
import com.sample.Constraint_Error.Job;
import com.sample.Constraint_Error.Modification;

rule "Insert Job"
    when
        p : Person()
        not Job(name == "Worker", holder == p)
    then
        insert(new Job("Worker", p));
        System.out.printf("Inserted Job for %s%n", p.getName());
end

rule "Retract Job"
    when
        j : Job(name == "Worker", h : holder)
        not Person(this == h)
    then
        retract(j);
        System.out.printf("Retracting Job for %s%n", h.getName());
end

rule "Moved away"
    when
        m : Modification(kind == "Moved away")
        p : Person(name == m.name)
    then
        retract(p);
        retract(m);
        System.out.printf("Person %s has moved away%n", m.getName());
end

rule "Invalid Modification"
    when
        m : Modification()
        not Person(b : dateOfBirth, getAge(b) < 200, name == m.name)
    then
        retract(m);
        System.out.printf("Received an modification that applies to no one%n");
end

function Integer getAge(Date dateOfBirth) {
    int add = 0;
    Date today = new Date();
    if (new Date(today.getYear(), dateOfBirth.getMonth(), dateOfBirth.getDay()).after(today)) {
        add = -1;
    }
    return today.getYear() - dateOfBirth.getYear() + add;
}

this issue occurs:

Execution is stopped on the last line to inspect the heap. According to the drl-file there should be no
person, job or modification object left in memory as all have been retracted and no references are
kept.

As this screenshot from VisualVM shows the person object (Alice) still lingers in memory.