compiled Python3 module produces error "dynamic module does not define module export function" - python-3.7

Question

I am trying to compile a Python package that I recently migrated from Python2 to Python3.
When running the source code in Python3 it works as expected, so do the source and compiled versions for Python2, but when I cythonize and compile the Python3 package the resulting binaries throw this error when importing a certain module:
dynamic module does not define module export function (PyInit_NKPD)
EDIT:
When I then close the Python interpreter, open it again and import the same model it works.
Interestingly when I put the code on my local drive it imports fine, but when I put it on my server and import it from there I get the above error. And to make matters worse, sometimes it imports fine from the server as well if I just wait a while and try again:
lockjaw:controller frank$ python3.7
Python 3.7.7 (v3.7.7:d7c567b08f, Mar 10 2020, 02:56:16)
[Clang 6.0 (clang-600.0.57)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import common
added to sys.path: /opt/ohufx/transfer/NUBRIDGE_COMPILE/osx/NKPD/src
trying to import model.NukepediaDB...
NukepediaDB imported
trying to import model.NKPD...
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "src/controller/common.py", line 15, in init controller.common
import model.NKPD # this does not import
ImportError: dynamic module does not define module export function (PyInit_NKPD)
>>> import common
added to sys.path: /opt/ohufx/transfer/NUBRIDGE_COMPILE/osx/NKPD/src
trying to import model.NukepediaDB...
trying to import model.NKPD...
NKPD imported
model.NKPD always seems to import fine, but model.NKPD seems to be the stumbling block, even though this may be a red herring. It almost behaves like sometimes the server connection drops out after the first import, though in that case the other incarnations (Python 2/source code) would throw errors as well (not to mention a whole lot of other things would break in my office).
I have reduced the package to three modules with nothing but import and print statements which can be found here (including the resuling C++ and binary files).
The structure is very simple:
Where common is the module I import to test by cd-ing into the src/controller folder, opening Python3.7 and importing common. Common then imports model.NukepediaDB and model.NKPD, the latter causing the trouble.
I cythonized the python files with this line:
/Library/Frameworks/Python.framework/Versions/3.7/bin/python3.7 py2cpp.py
Then compiled with this:
/Library/Frameworks/Python.framework/Versions/3.7/bin/python3.7 setup.py build_ext --inplace
I would love to understand why the import sometimes fails when run from the server, as I have to distribute this package to others and need to ensure it runs reliably.
Thanks,
Frank