http-proxy-middleware econnreset error after successful post request

Developing a contact form using Nodejs/Express and create-react-app following this tutorial https://www.youtube.com/watch?v=o3eR0X91Ogs. The issue that I'm running into is that when I hit submit on the form the message succeeds, and I get it in my inbox. However, in the developer console, I am hit with the timeout error I set on the axios.post located in Contact.js, and in my terminal it logs message sent, console log located in index.js, immediately throwing the following error afterward:

HPM ERROR: Error: socket hang up
[1]     at connResetException (internal/errors.js:612:14)
[1]     at Socket.socketCloseListener (_http_client.js:443:25)
[1]     at Socket.emit (events.js:326:22)
[1]     at TCP.<anonymous> (net.js:673:12) {
[1]   code: 'ECONNRESET'
[1] }
[1] [HPM] Error occurred while trying to proxy request /api/contact/ from localhost:3001 to http://localhost:3000/ (ECONNRESET) (https://nodejs.org/api/errors.html#errors_common_system_errors)

Does anyone know why this error is occurring, and how I can fix it? The message sends but hangs afterward which prevents the app state from resetting (resetForm). At the same time, the axios.post in Contact.js doesn't update the state of sent to true.

The Github repo for the project.

Edit: I've been stuck on this for a few days now. Looked at similar questions, attempted ALL the fixes I could find, and this error still persists.

from http-proxy-middleware econnreset error after successful post request