Original thread was getting really messy with 3rd party acting as intermediaries and turning off-topic so it's moved to a dedicated thread with direct input/feedback from system's owner.
As previously indicated/provided by @Jake Lo:
Dortania guide :
https://dortania.github.io/OpenCore-Post-Install/usb/misc/shutdown.html
You'll need both of the *.aml files and add the 2 patches to your config.plist
Jake provided the files in the following attachment:
ShutdownFix.zip
@Mr_T_aus_B please list your system's specs, ideally add them in signature.