I think I've found a way to get some additional information on why the error is occurring.

Run the uup_download_macos.sh script once, allowing it to download the component files from Microsoft. It will fail but leave the files that it downloaded in a sub-folder called UUPs.

You'll also find a sub-folder named "files". Within that folder is a script called "convert.sh". Open that with your favorite editor.

On line 426 of the file, it reads:

 cabextract -d "$extractDir" "$file" >/dev/null 2>/dev/null

Change that to read:

 cabextract -d "$extractDir" "$file" >>cabextract.out 2>>cabextract.err

Save and close the file.

Make sure your working directory is the one that contains the uup_download_macos.sh script, and run following command to restart the conversion of the downloaded files:

files/convert.sh

When the process fails again, you'll find two files cabextract.out and cabextract.err. The cabextract.err file may give a clue as to why the process is failing.