This was a file on a hard drive I was using during a transition from Windows 7 to 10. I couldn't access it using Windows Explorer for some reason? The (E:/Windows/Assembly/) path wasn't a filesystem I could browse through using Explorer, but for some reason I could use Firefox to navigate to it and download the offending file. I'm not really sure what it is but it showed up in the report whenever I moved the file somewhere and scanned that directory. The scan had other detections, but those were Firefox user.js preferences and I removed them from the report because those were intentional and also on a different drive.
FPreport.txt
Microsoft.DiaSymReader.ni.zip