WMFong

Since I have no idea if the problem is coming out from the game or rage plugin hook, I will suggest you to do the following something to check if the problem is coming out from the game or the other things. 1. Open GTA5 without using rage plugin hook. If this work, it means the problem isn't because of the game. 2. Restart the computer. (Might help, but most of the time didn't, but it is worth for a try) 3. Check whether there is any antivirus that you forgot to disable. Check it from the setting>apps (Sometimes some apps installed to your computer without asking you yes or no, so I suggest checking it)

Did you just install addon cars or something like that into the game? Last time I experience this was because of not installing the gameconfig after installing the addon vehicles

It's out already. Check it in this link.

Could be the issue from the GTA V game. Don't really experience the issue, but bugs will start to increase after 30 minutes. That might be the reason why the Rendering becomes bad after some time. Hope this information helps you. And good luck on fixing it.

Don't you have the key.ini file?

Try to restart the Rage Pingin Hook after disabled your anti virus

How?