Animated Flipbook Mask gets blurry

Hey there,
I’m creating a game where the character has 2D Textures as Eyes. They eyes consist of 4 Planes: 2 Planes in front for the eye lid/lashes and 2 planes behind for the iris ( so that I can seperately move them ). Now everything works well except the animation: I figured I use a FlipBook function in the material to animate the eye blinking. Though, while it animates it looks blurry/pixelated and kind of washed out. But only shortly after the animation. See this video:

My material is set to be masked and I’m using an instanced version of it. I attached a screen of my iris material as well.
Does anyone know how to solve this problem? I wondered if it has something to do with mipmaps but I disabled them for the texture and the problem remains. The further the camera is away the worse it gets.

Thanks!

Check anti-aliasing in project settings - > rendering