Point light illuminating half of scene

My point light is illuminating only half of the scene on my small 3D renderer. It happens on every scene I've tried (conference room, cornell box, etc). How do I go about debugging this? What could be wrong? I feel like I've tried everything but nothing helps.

Here's the shaders. I'm not doing anything out of the ordinary. 

//
// VERT SHADER
//
#version 410 core
 
uniform mat4 M;
uniform mat4 V;
uniform mat4 P;
 
layout (location = 0) in vec3 position;
layout (location = 1) in vec3 normal;
layout (location = 2) in vec3 color;
layout (location = 3) in vec2 …