Further to this below, I am seeing the same behaviour if I use ipy.exe - in the 2.7 version I can debug sub-folders/files, but not in version 3.4

I work in an environment where IronPython is hosted in a .NET executable.
When the environment was based on v2.7, I could split my code into packages, and use VS2017 to debug with breaklines, inspections in any file.
Now the environment is based on v3.4, I can only use breakpoints in the top level script, not any package sub-files.
Can anyone advise what might be causing this behaviour.

I have written a lightweight .NET app which demonstrates the problem.
App has references to IronPython, IronPython.Modules, Microsoft.Dyamic and Microsoft.Scripting

If I reference these libraries from IronPython2.7 then everything executes as expected (the string "Hello Wyn" appears in the textbox), and I can place breakpoints in any of the python files

When the libraries are referenced from IronPython3.4 then the code still executes as it should, but now I can only place breakpoints in the MyScript.py file. The ones in the other python files are ignored.

Please can anyone help - I am guessing something has changed between v2.7 and v3.4 but I don't really know where to start looking to try to solve the problem.
Many thanks

The engine is setup as

    Dictionary<string, object> options = new Dictionary<string, object>();
    options["Debug"] = true;
    m_engine = Python.CreateEngine(options);
    m_scope = m_engine.CreateScope();
    m_scope.SetVariable("txtOutput", txtOutput);
    ScriptSource source = m_engine.CreateScriptSourceFromFile(scriptFileName);
    source.Execute(m_scope);

my python structure is
MyScript.py
/MyPythonPackage/init.py
/MyPythonPackage/PythonClass.py

init.py:

from .PythonClass import PythonClass

PythonClass.py:

class PythonClass(object):
    """description of class"""
    def __init__(self, textBox):
        self.textBox = textBox
    def execute(self, name):
        self.textBox.Text = "Hello {}".format(name)

MyScript.py:

import sys
from MyPythonPackage import PythonClass

cls = PythonClass(textBox=txtOutput)
cls.execute("Wyn")