Issue with my Asus RT-AC66U with Merlin 374.43

[RMerlin]

Yes, really weird. But I'm really starting to be conviced that it's LoL related.

It's still solid (router), and no games played so far. What I find strange is not the WiFi dropping, but the whole router reboots, all connections gets dropped. My son's computer is wired, he has a workstation.

He will surely play in about 6-7 hours, so if it crashes, we will know.

Try disabling uPNP support in the router, in case it's an issue with LoL's port forwarding requests. That's one thing I could see that would be application-specific, and would explain why the crashes only occur with that game in particular.