OpenGL cannot read framebuffer attachment when there are only 3 components, but can read when there's 4 component

I'm currently working on deferred rendering in OpenGL, and I'm currently trying to pass position and normal data from the geometry pass to the lighting pass.

However, any framebuffer attachments that aren't of type GL_RGBA give empty values when read as a texture. I've managed to boil it down to the fact that any framebuffer attachments that do not have 4 components simply do not work.

How can I fix this? What am I missing?

C++ Code:

// Geometry Buffer
gbuffer::gbuffer(uint32_t _width, uint32_t _height) {
    // Create GL buffer.
    glCreateFramebuffers(1, &handle_);

    // Colour attachments.
    colour_attachments_.resize(num_gbuffer_attachments);
    colour_attachments_[gbuffer_position] = std::make_shared<texture_2d>("position", _width, _height, GL_RGB16F); // Only 3 components, does not work.
    colour_attachments_[gbuffer_normal] = std::make_shared<texture_2d>("normal", _width, _height, GL_RGB16F); // Only 3 components, does not work.
    colour_attachments_[gbuffer_albedo] = std::make_shared<texture_2d>("albedo_colour", _width, _height, GL_RGBA8); // 4 components, no problem.
    colour_attachments_[gbuffer_specular] = std::make_shared<texture_2d>("specular_colour", _width, _height, GL_RGBA8);  // 4 components, no problem.
    colour_attachments_[gbuffer_gloss] = std::make_shared<texture_2d>("gloss", _width, _height, GL_R32F); // Only 1 component, does not work.
    for (auto i = 0; i < colour_attachments_.size(); ++i) {
        glNamedFramebufferTexture(handle_, GL_COLOR_ATTACHMENT0 + i, colour_attachments_[i]->handle(), 0);
    }

    // Depth-Stencil attachments.
    depth_stencil_attachment_ = std::make_shared<texture_2d>("depth_stencil", _width, _height, sized_format::depth24_stencil8);
    glNamedFramebufferTexture(handle_, GL_DEPTH_STENCIL_ATTACHMENT, depth_stencil_attachment_->handle(), 0);
}

GLSL Code:

uniform sampler2D u_texture_gbuffer_position;
uniform sampler2D u_texture_gbuffer_normal;
uniform sampler2D u_texture_gbuffer_albedo;
uniform sampler2D u_texture_gbuffer_specular;
uniform sampler2D u_texture_gbuffer_gloss;

const vec3 position = texture(u_texture_gbuffer_position, io_tex_coord.xy).rgb; // All zeros.
const vec3 normal = texture(u_texture_gbuffer_normal, io_tex_coord.xy).rgb; // All zeroes.
const vec4 albedo = texture(u_texture_gbuffer_albedo, io_tex_coord.xy); // Has correct values.
const vec4 specular = texture(u_texture_gbuffer_specular, io_tex_coord.xy); // Has correct values.
const float gloss = texture(u_texture_gbuffer_gloss, io_tex_coord.xy).r; // All zeroes.

I fixed the issue. GL_BLEND was enabled, which means that any fragments with an alpha value of 0 is essentially discarded.

So even though I was writing to a texture with only 1 or 3 components, because by default their alpha value was 0.0f, even their RGB value was discarded for some reason.

So the solution was to disable GL_BLEND during my geometry pass to ensure that all textures are written to correctly without their values being discarded.