Post processing shader occludes SubViewport

Help Shaders
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1

I was making a diegetic UI in my Godot game, applied a post processing filter to my game using a Spatial shader, but for some reason, the mesh containing the SubViewport gets hidden as soon as the camera faces it. Does anyone know why does this happen by any chance? Examples of what’s happening:
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2

it might have been the range

3

Nope, apparently it’s a thing that goes on with Sprite2Ds and Quadmeshes, as soon as I tried inserting a material inside of a normal mesh, it started working as intended. my theory is it doesn’t support meshes with only 4 vertex, but I might (and probably am) wrong.

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