In attempting to download a mandatory update for Playstation All-stars Battle Royale (specifically the 1.08 update), it will hang on 99% (either one or two seconds left) for around a minute or so. Afterwards, I always get this message: "An error has occurered during the download operation. (80710723)"
This has happened a couple of times before, but usually I just have to retry once or twice and it will work. I have literally tried around ten times and every result has been exactly the same. I've restarted my router multiple times after looking it up on my own to no avail.
I've also noticed that in the threads made a couple years ago that I have recently looked up, they had said many people were suddenly having a similar problem. However, I can't find anyone else having the problem currently.
Since you said router, you're using a WiFi connection for your console - correct?
Reset both modem/router if you only did one.
If you are wireless, have you tried using a wired connection? How strong is your signal strength and long does it take to download all the way to 99% and then stopping? It may be timing out. Have you been getting signed out of PSN lately or any other disconnection issues.