FireFox will corrupt the files too.
Use IE or the Torrent if you can.
if you can use an outisde program thats the most advisable to do, such as IDM or JDownloader among many others. note that IDM is a paid software, unless u crack it, thats up to u and ur own choice, jdownloader is a free to use software, the diference is tha tIDM is also an accelarator, it will boost ur download speed.
after you download the .rar file please do the following steps:
1. create a new folder with a diferent name than any other previous related to EpicPW, for exmaple if you previously had a folder named: EpicPW now create a new folder name for exmaple: EPW
2. before extracting go to your windows defender and add the new folder you created to the exception list
3. use 7zip to extract the game into the new folder
4. double click the patcher.exe
enjoy