Hot module reloading with proxy not working in Firefox but works in Chrome

Created by: andygock

Hi,

When developing using create-react-app in Firefox 66.0.1, hot module reloading isn't working, and I get this error in console when using npm run start:

The connection to ws://localhost:3000/sockjs-node/800/q2e1i5qh/websocket was interrupted while the page was loading. websocket.js:7

This doesn't happen in Chrome, and HMR works there as expected. I didn't have problems in the past with Firefox, I'm not sure if it's triggered by a Firefox update, or new versions of react-scripts. It may even be specific to my app.

I'm using react-scripts versions 2.1.8

Does anyone know what would cause this, and how I could get HMR working again? I'm not really sure where to look.

Thanks