I would also delete everything from the Products folder just in case there is already something in there that is corrupted.
C:\ProgramData\Microsoft\Packages\Products\RM-1096
were the RM-xxx number is your phone version. Delete the entire RM-xxxx folder and try the Windows Device Recovery Tool again. If you do have a slow, shaky internet connection as Chintan commented, you may not want to do anything else on the PC until the download is finished. The download is about 2Gb in size.
Another thing I'd try if there is a different PC or laptop around to try it on that.
Good luck