Strange flashing cube bug in snake game

I'm trying to make a simple snake game in C and OpenGL, and I have this at the moment, which runs almost perfectly:

#include "glad/glad.h"
#include <GLFW/glfw3.h>

#include "stb/stb_image.h"

#include <stdio.h>
#include <time.h>
#include <stdlib.h>

#include "cglm/cglm.h"
#include "cglm/call.h"

#include "apple.h"
#include "snake.h"

struct Snake snake;
snakeDir dir;

void initSnake() {
    dir = Up; //Initilize direction

    snake.speed = 15;
    snake.size = 1;

    snake.body[0].x = -1.0f;
    snake.body[0].y = -1.0f;

    snake.head = snake.body[0];

    snake.ticks = 0;
}

static void _drawSnake() {

    snake.ticks++;

    if (glfwGetKey(window.self, GLFW_KEY_UP) == GLFW_PRESS && dir != Down)
        dir = Up;
    if (glfwGetKey(window.self, GLFW_KEY_DOWN) == GLFW_PRESS && dir != Up)
        dir = Down;
    if (glfwGetKey(window.self, GLFW_KEY_LEFT) == GLFW_PRESS && dir != Right)
        dir = Left;
    if (glfwGetKey(window.self, GLFW_KEY_RIGHT) == GLFW_PRESS && dir != Left)
        dir = Right;


    if (snake.ticks == snake.speed) {
        // Move the snake's head in the direction specified by the dir variable
        switch(dir) {
            case Up:
                snake.head.y -= 2.0f;
                break;
            case Down:
                snake.head.y += 2.0f;
                break;
            case Left:
                snake.head.x -= 2.0f;
                break;
            case Right:
                snake.head.x += 2.0f;
                break;
        }

        // Move the snake's body
        for (int i = snake.size - 1; i > 0; i--) {
            snake.body[i] = snake.body[i-1];
        }

        snake.body[0] = snake.head;
        
        // Reset ticks
        snake.ticks = 0;
    }

    // Check if the snake eats an apple
    if (snake.head.x == apple.x && snake.head.y == apple.y) {
        // Generate a new apple
        int rx = (rand() % (10 + 1 + 8) - 8);
        int ry = (rand() % (10 + 1 + 8) - 8);
        float ax = (rx + rx % 2) - 1.0f;
        float ay = (ry + ry % 2) - 1.0f;

        apple.x = ax;
        apple.y = ay;

        snake.size++;
    }

    // Check if the snake hits its own body
    for (int i = 1; i < snake.size; i++) {
        if (snake.head.x == snake.body[i].x && snake.head.y == snake.body[i].y) {
            terminateWindow();
        }
    }
}

void renderSnake(struct Shader shader) {

    glActiveTexture(GL_TEXTURE0);
    glBindTexture(GL_TEXTURE_2D, snake.texture);

    useShader(shader);

    glBindVertexArray(snake.VAO);

    for (int i = 0; i < snake.size; i++) {
        glm_mat4_identity(camera.model); //Reset matrix
        glm_rotate(camera.model, glm_rad(90.0f), (vec3) {1.0f, 0.0f, 0.0f});
        glm_scale(camera.model, (vec3) {0.1, 0.1, 0.05}); //Construct second matrix
        glm_translate(camera.model, (vec3) {snake.body[i].x, snake.body[i].y, -21.0f});
        setShaderMat4(shader, "model", camera.model);

        glDrawElements(GL_TRIANGLES, 36, GL_UNSIGNED_INT, 0);
    }

    _drawSnake();
}

The only problem is that whenever the snake collects an apple, it looks like the head of the snake or something flashes in the middle of the screen for a second then disappears. I tried tracking this bug down but I can't figure out what it's coming from. This is what it looks like:

Does anyone know what bug in my code is causing this? It's really quite annoying and any help is greatly appriciated!