Visual bug/artifact when using varying UV offset in a (distortion) shader in Godot 4.2+ mobile renderer

[11811341]

Tested versions

Reproducible in Godot 4.2 and above using the mobile renderer. NOT present in 4.1

System information

Windows 10, mobile renderer, Godot 4.2.1

Issue description

When a distortion shader is applied to a plane that uses a varying UV offset to create the distorted effect, a triangular patch of "roughness" appears in the portion opposite the camera. This problem was not present in Godot 4.1x.

Video of the issue can be seen here:
https://www.reddit.com/r/godot/comments/1c5sd1z/day_2_of_seeking_help_with_shader_bugged_by_42/

Image from the MRP, undesirable area circled red:

Steps to reproduce

1. Use Godot 4.2 or above
2. Use mobile renderer
3. Basic scene setup for better visibility (Light & Environment, these don't affect the bug, but make it more easily visible)
4. Set up a plane and create and apply a new Shader material
5. Use the following minimal shader code:

shader_type spatial;

uniform sampler2D SCREEN_TEXTURE : hint_screen_texture, repeat_disable;

uniform float refraction_strength = 0.05;
uniform sampler2D refraction_noise;

void vertex() {
}

void fragment() {
vec2 offset = texture(refraction_noise, UV).rg;
offset = 2. * offset - 1.;
offset *= refraction_strength;
vec2 ouv = SCREEN_UV + offset;
ALBEDO = texture(SCREEN_TEXTURE, ouv).rgb;
}

Minimal reproduction project (MRP)

Bugfinding.zip

[clayjohn]

This might be a duplicate of #88786. It seems the issue doesn't occur on all devices, what CPU and GPU are you testing on?

[11811341]

Yeah it definitely looks that way... It looks even more similar to the other one you linked (#88585).
It shows up on my intel i7-6700k GTX1070, as well as on my honor 50, as well as an honor 90 phone.
Would be really sus if it was a device issue.