PUT request with Multipart/form-data fails only in firefox

Question

I've tried this on Edge, Chrome and Opera and my upload works fine, the problem happens ONLY on firefox:

From the front end, I send a multipart/form-data request like so:

         $.ajax({
                    url: `/api/myUpdate/${$scope._id}`,
                    method: 'PUT',                  
                    data:formData,
                    contentType:false,
                    processData:false,
                    cache:false, 
                    success: response =>{
                        ..
                    },
                    error: err =>{
                        ..
                    }
                })

Then on my nodeJs server:

Route:

var multiparty = require('connect-multiparty');
    var multipartyMiddleware = multiparty({maxFieldsSize:'200mb'});
    app.route('/api/myUpdate/:_id')
        .post(users.requiresLogin, multipartyMiddleware, hasAuthorization, myUpdateFn);

When debugging, i get through my requireslogin Middleware, but it gets stuck in multipartyMiddleware, it never reaches "hasAuthorization" or "myUpdateFn".

When the request times out, I get this output error on the server

Error: Request aborted
    at IncomingMessage.onReqAborted (C:\dev\eedweb\node_modules\multiparty\index.js:190:17)
    at IncomingMessage.emit (events.js:182:13)
    at abortIncoming (_http_server.js:449:9)
    at socketOnClose (_http_server.js:442:3)
    at Socket.emit (events.js:187:15)
    at TCP._handle.close (net.js:610:12)

From the debugging I've done it seems to get stuck in a file called "async_hooks"... but I don't really understand what that even does.

I've tried with varying upload sizes and it doesn't seem to affect the outcome.

There are no error messages on the front end, and the Firefox inspector doesn't show anything other than the header in the network tab, but the formdata object seems to be the same across browsers and when I inspect the object in the node server there seems to be a message body, params, files etc. firefox just doesn't seem to show it in the network inspector.

Am I doing something wrong?