My fiancée’s TP-Link TL-WR841ND (v9) router was systematically crashing when under heavy load, especially with Torrent. It was only possible to return the router to operation by power cycling it. I had tried to update its firmware with the newest version avalaible from TP-Link’s website. Nonetheless, it was not enough to solve the presented issue.
In order to avoid launching this router through the 4th floor window, as last resort I tried to reflash it with OpenWRT. Here is the wiki page dedicated to this cheap router: https://wiki.openwrt.org/toh/tp-link/tl-wr841nd. As far as I can tell its been a success! The router isn’t crashing anymore under heavy load. On top of that, OpenWRT is a full featured GNU/Linux distribution! Super cool! Besides that, its gui management provides much more features than the stock firmware from TP-Link.
To wrap it up, if your TP-Link TL-WR841ND is crashing just reflash it OpenWRT. You will no regret by no means.