Sometimes routers just get faulty. I’ve found it just makes more sense to replace them. Repairs aren’t likely or worth getting repaired.
Also the expensive gaming routers don’t make much sense. Mesh is generally better than a single fast router for WiFi. A balance of multiple access points get a more reliable speed all over than a single fast point.
You can get a decent TP-Link Deco setup for pretty cheap. Wired for any stationary devices. Wired backhaul is better for Mesh if possible, otherwise at least a separate wireless backhaul channel.
If you want to spend the money. There’s more professional solutions which are really rock solid. With a managed switch and matching access points. But these are complex to configure. They also have good built in VPN functions.
The system requirements of Outlast appear to be really low. Something like a Core 2 Duo @2.2ghz or even some 2000s era 2.2Ghz Athlon dual core. You’re using an 8th gen i5. Which is much faster per core. You probably aren’t even going to hit the modest 1.8Ghz turbo boost limit your manufacturer placed. I expect that you’re mostly maxing out the integrated graphics before hitting framerates which max out your CPU.