GStreamer build windows cant import _giscanner - python-3.x

Question

I'm trying to build GStreamer on windows using gst-build.
My environment:
Visual studio 2019 Professional
Python 3.9 64 bit
Meson 0.58.999
Ninja 1.10.2
the error message is:
>ninja -C build
ninja: Entering directory `build'
[1/30] Generating gir-glib with a custom command (wrapped by meson to set PATH)
FAILED: subprojects/gobject-introspection/gir/GLib-2.0.gir
[long list of python subprocess args with include patsh, c files etc]
Traceback (most recent call last):
File "C:\Work\GStreamer-build\source\gst-build\build\subprojects\gobject-introspection\tools\g-ir-scanner", line 98, in <module>
from giscanner.scannermain import scanner_main
File "C:\Work\GStreamer-build\source\gst-build\build\subprojects\gobject-introspection\giscanner\scannermain.py", line 35, in <module>
from giscanner.ast import Include, Namespace
File "C:\Work\GStreamer-build\source\gst-build\build\subprojects\gobject-introspection\giscanner\ast.py", line 29, in <module>
from .sourcescanner import CTYPE_TYPEDEF, CSYMBOL_TYPE_TYPEDEF
File "C:\Work\GStreamer-build\source\gst-build\build\subprojects\gobject-introspection\giscanner\sourcescanner.py", line 35, in <module>
from giscanner._giscanner import SourceScanner as CSourceScanner
ImportError: DLL load failed while importing _giscanner: The specified module could not be found.
ninja: build stopped: subcommand failed.
if I check the build directory:
So the file does build, but for some reason can't be imported.
I've seen from here that there were some changes to python 3.8 in how DLLs are searched for, but even if I manually open a python prompt in the parent directory and add both the parent and the giscanner directories to sys.path and using os.add_dll_directory I still can't import the module:
>>> import os,sys
>>> a = os.add_dll_directory(os.getcwd())
>>> a
<AddedDllDirectory('C:\\Work\\GStreamer-build\\source\\gst-build\\build\\subprojects\\gobject-introspection')>
>>> b = os.add_dll_directory(os.path.join(os.getcwd(),'giscanner'))
>>> b
<AddedDllDirectory('C:\\Work\\GStreamer-build\\source\\gst-build\\build\\subprojects\\gobject-introspection\\giscanner')>
>>> sys.path.insert(0, os.getcwd())
>>> sys.path.insert(0, os.path.join(os.getcwd(),'giscanner'))
further digging shows that pkg-config doesn't seem to know where to find gio, however that was also built sucessfully as part of the build so not sure why it doesn't know.

Answer 1

Unsure the actual problem, but the workaround is to revert Python to 3.7.9 (64 bit)
https://www.python.org/downloads/release/python-379
Its also been suggested you can build without that component using
-Dintrospection=disabled