ADDITIONAL SYSTEM INFORMATION :
Centos 7.6, OpenJDK 11.0.2.

A DESCRIPTION OF THE PROBLEM :
The entire problem and sample is written up at https://stackoverflow.com/questions/58052667/intheritance-at-package-visibility-in-java

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Please see: https://stackoverflow.com/questions/58052667/intheritance-at-package-visibility-in-java

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The inheritance does not follow into packages E and F:

((A)a).m();
A
((A)b).m();
A
((A)c).m();
A
((A)d).m();
D
((A)e).m();
D
((A)f).m();
D
((D)d).m();
D
((D)e).m();
D
((D)f).m();
D
ACTUAL -
Note that E and F values around the middle:

((A)a).m();
A
((A)b).m();
A
((A)c).m();
A
((A)d).m();
D
((A)e).m();
E
((A)f).m();
F
((D)d).m();
D
((D)e).m();
D
((D)f).m();
D

---------- BEGIN SOURCE ----------
package a;

public class A {
    void m() { System.out.println("A"); }
}

// ------ 

package b;

import a.A;

public class B extends A {
    void m() { System.out.println("B"); }
}

// ------ 

package c;

import b.B;

public class C extends B {
    void m() { System.out.println("C"); }
}

// ------ 

package a;

import c.C;

public class D extends C {
    void m() { System.out.println("D"); }
}

// ------ 

package b;

import a.D;

public class E extends D {
    void m() { System.out.println("E"); }
}

// ------ 

package c;

import b.E;

public class F extends E {
    void m() { System.out.println("F"); }
}

// --------

package a;

import b.B;
import b.E;
import c.C;
import c.F;

public class Main {

    public static void main(String[] args) {
        A a = new A();
        B b = new B();
        C c = new C();
        D d = new D();
        E e = new E();
        F f = new F();

        System.out.println("((A)a).m();"); ((A)a).m();
        System.out.println("((A)b).m();"); ((A)b).m();
        System.out.println("((A)c).m();"); ((A)c).m();
        System.out.println("((A)d).m();"); ((A)d).m();
        System.out.println("((A)e).m();"); ((A)e).m();
        System.out.println("((A)f).m();"); ((A)f).m();

        System.out.println("((D)d).m();"); ((D)d).m();
        System.out.println("((D)e).m();"); ((D)e).m();
        System.out.println("((D)f).m();"); ((D)f).m();
    }
}
---------- END SOURCE ----------

FREQUENCY : always