Having Trouble Restoring OS to Unihiker

I've been trying to restore the OS to a malfunctioning Unihiker as per the instructions on https://www.unihiker.com/wiki/burner, but when I get to step 3.1 (Load OS File) and it does the md5 verification, I get a message saying the image I download in step 2 is damaged. Has anyone else had this problem or there is another source for the system image file?