I have experienced this before. I found that loading the launcher in administrator mode and just keep re-trying eventually lets it pull through. It also helps that you have a wired internet connection just in case wifi cuts out for whatever reason. Good luck.
Happening to me as well. Get stuck at 33% while applying patch. It chokes/freezes my computer I can't even use my browser. I let it be for more than an hour but no movement. Launcher already run as admin. Never happened to me before.