The copy operation can indeed lead to corruption, for instance if you managed to copy before everything downloaded. I understand sometimes people do this due to file size etc. but it is really unsafe and you risk more by doing this. SW is the only official way to get the mods at this point. We have stopped own updater and torrent distributions and cannot be responsible for the integrity of the files if you get them from anywhere else, or use them in any way other than the standard subscription mechanism in SW.