I can confirm that that unit_stats_land opens fine on my computer, which is also running Windows 10. The first two things I can think of are that something might be missing from your installation of the .NET Framework (PFM uses the .NET Framework 4.0, but newer versions should also be compatible) from when you either updated to a new operating system or changed computers or that something happened to the data.pack file you are trying to edit. I would try reinstalling the .NET Framework and checking to see if PFM can open the files in a different pack file.