(CRASH) Game Freezes/Visual Bugs

Hello, I come to you because I think I have tried everything, after the last patch (5.8), I've experienced 2 issues:

1. randomly, I'll get a visual bug similar to the one spirit guard udyr had, where a long black line would appear, link for reference https://www.youtube.com/watch?v=Sb3XrcD_osc It is very similar, but the "line" is less strong and it appears randomly in my champ or others, and it only goes away if i press alt+tab and go back to the game. (but this is not the issue that annoys me the most, since it can be "fixed" easily by doing what i said" This appears in every game now.

2. My game freezes randomly, I don't get frame drops as far as I know, my fps are always at 60fps, if anything, they drop to 40-50 in team fights. After this patch, my game will just randomly freeze, at first the screen would look just like a 2 seconds gif of the moment it froze, if that makes sense, but after some games, the screen just turns completely black, sometimes I can fix it just by alt+tab and then come back to the game, but other times it would take 30 seconds or 1min to fix itself and return to normal. This appears in every game now.

Also, I looked through this board and spotted 2 discussions similar to this, both of them got no reply from Riot or solved at all, so hopefully someone here knows what to do. http://boards.na.leagueoflegends.com/en/c/help-support/gQAQp64W-random-freezes-in-game http://boards.na.leagueoflegends.com/en/c/bug-report/EHBmBdhF-gameplay-random-freezes-late-game

This has been bothering me for the past days, I don't know what to do, I've done: Updated my drivers, nvidia and intel both say my drivers are up to date, I repaired the game, after that I played a game and it wasn't fixed, so I uninstalled and installed it again, and it's still happening, please I'm desperate and need guidance.

P.S. I already contacted Riot Support and the person that replied wasn't very helpful, they asked me to post about this "bug" here.