the world doesn't render correctly when I have a robot rendered

[ff66theone]

Yesterday, I wanted to make a robot to make it autonomous and see what happens. but as soon as I assembled it, the world started to flicker when I don't watch the world directly. I thought it was the Optifine mod so I removed it. When I joined the world, the rendering was completely destroyed ! Only OpenComputers blocks rendered so I had to put the robot in a chest because that is the only way to make the world render normally :(

note that i have also fastcraft mod because i am on a potato computer