Landscape texture artifacts when using Texture Atlas

Hello. I am a student game designer who has recently transferred from Unity into Unreal Engine. I am still quite new but I simply cannot find help on this specific topic. I have searched everywhere and looked through the forums but I am unable to find a working solution for this problem. I am developing an open-world game with landscapes and I am using texture atlases to store multiple textures. For some reason, the texture results have major artifacting on the terrain even after using a custom node below. I think it is caused by mipmapping but I am not entirely sure how to get the desired effect.

return Tex.SampleGrad(TexSampler,UV,ddx(UV1),ddy(UV1));

I am using an AtlasSplitter4x4 node to output the sections of the atlas into landscape layer textures.