Artifacts in my displacement shader

Question

I'm using this shader for a Shockwave effect

shader_type canvas_item;

uniform float tile_factor = 1.0;
uniform float aspect_ratio = 1.0;
uniform sampler2D uv_offset_texture : hint_black;
uniform vec2 uv_offset_size = vec2(1.0, 1.0);
uniform float size = 0.02;

void fragment() {
    vec2 waves_size = vec2(size, size);
    vec2 offset_texture_uvs = UV * uv_offset_size;
    vec2 texture_based_offset = texture(uv_offset_texture, offset_texture_uvs).rg;
    texture_based_offset = texture_based_offset * 2.0 - 1.0;
    vec2 adjusted_uv = UV * tile_factor;
    adjusted_uv.y *= aspect_ratio;
    vec2 cPos = -1.0 + 2.0 * UV / (1.0 / TEXTURE_PIXEL_SIZE);
    float cLength = length(cPos);
    vec2 uv = FRAGCOORD.xy / (1.0 / SCREEN_PIXEL_SIZE).xy + 0.0;
    COLOR = texture(SCREEN_TEXTURE, uv + texture_based_offset * waves_size);
}

With high resolution doesn't look that bad

But with my wanted pixel-art resolution gives this ugly blurry artifacts.

I'm not sure if it's a rendering-configuration problem or if I may need some adjustments to the shader.

Any help is welcomed!