Order Management not working - mainfest loaded as stylesheet & data.map not a function

On latest Customised Commerce the Order Management screen does not load correctly as I think the manifest isn't loaded (Latest Chrome, Firefox etc)

1. Error in console (firefox only)

The stylesheet https://www.example.com/EPiServer/EPiServer.Commerce.UI.CustomerService/14.19.0.0/clientResources/build/manifest.json was not loaded because its MIME type, "application/json", is not "text/css". 

This can be verified by looking at the html source : view-source:https://www.example.com/EPiServer/Commerce/OrderManagement

<link href="/EPiServer/EPiServer.Commerce.UI.CustomerService/14.19.0.0/clientResources/build/manifest.json" rel="stylesheet" />

2. The following error also occurs in the browser (Latest Chrome, Firefox etc)

Chrome:
main.js:1 Uncaught (in promise) TypeError: t.sent(...).data.map is not a function
    at t.<anonymous> (main.js:1:11925)
    at main.js:1:11404
    at Object.next (main.js:1:11509)
    at i (main.js:1:10246)
Firefox:
Uncaught (in promise) TypeError: t.sent().data.map is not a function
    p https://www.example.com/EPiServer/EPiServer.Commerce.UI.CustomerService/14.19.0.0/clientResources/build/static/js/main.js:1