I think I’ve found the problem. It seems like you’re not supposed to unzip/extract osx-unsigned on Windows, as it ruins filepaths.
Here’s a different workaround, but it won’t work as the NWJS version provided is way too old. I might have to do that step for you and then upload the file. The steps are similar: edit package.json, download Normal NWJS (from me?), but instead of exporting the Mac version, you export the Web version instead, then place all your files into a specific folder in the zip without extracting it.
That’s a bit annoying. I thought MV only had a problem with newer Macs, but the Mac export button doesn’t actually work to begin with if you’re on Windows? I wonder if MZ has the same problem as well.