Firebase cloud functions not updating when deployed - still serving old version of function

I'm frustrated and confused. I'm trying to deploy my cloud functions but whenever I do they're not updating properly and despite firebase saying that they were updated successfully, keep serving the old function. Here's my index.js:

const functions = require('firebase-functions');
const admin = require('firebase-admin');

//Cloud functions for user interaction
const charge = require('./func/charge');
const addProduct = require('./func/addProduct');
const removeProduct = require('./func/removeProduct');
const updateTracking = require('./func/updateTracking');

admin.initializeApp(functions.config().firebase);

exports.charge = functions.https.onRequest(charge);
exports.updateTracking = functions.https.onRequest(addProduct);
exports.addProduct = functions.https.onRequest(removeProduct);
exports.removeProduct = functions.https.onRequest(updateTracking)

And here's my addProduct function with everything stripped away. This still doesn't update.

const functions = require('firebase-functions');
const admin = require('firebase-admin');
const express = require('express');
const request = require('request');
const send = require('../send.js');
const cors = require('cors')({origin: '*'});

function addProduct(req, res) {
    console.log('THIS NEVER PRINTS')
    send(res, 500, {
        error: `FAILURE`
    })
}

const appAddProduct = express();
appAddProduct.use(cors);
appAddProduct.post('/', (req, res) => {

    // Catch any unexpected errors to prevent crashing
    try {
        addProduct(req, res);
    } catch(e) {
        console.log(e);
        send(res, 500, {
            error: `The server received an unexpected error. Please try again and contact the site admin if the error persists.`,
        });
    }
});

module.exports = appAddProduct

This is still serving up a success message & status code 200 from an older function with a logic error in it when this should just be serving up a 500 error every time. Something is clearly wrong with the way I've split this into multiple files as that is where the trouble started but I'm not sure where I've gone wrong. Help would be much appreciated.