issue with javascript loading - spring cloud gateway route to downstream page

Question

I was migrating a project from zuul to spring cloud gateway, and need to route a call to a web portal UI. The routing works and I got the index page of portal UI back.

However, comparing with the result from zuul, the page is blank, even though page source is identical to the page getting back from zuul. The reason relates to the page containing certain reference to some javascript.

e.g. <script src="/home/dist/app.bundle.1e78ceebf1b08da0218d.js"></script>

from the portal UI log, I can see spring cloud gateway was calling portal UI explicitly referring to this js -

Requested URL: [http://host.docker.internal:8553/app.bundle.1e78ceebf1b08da0218d.js]

in zuul: chain.doFilter(request, response); while parameter is HttpServletRequest, HttpServletResponse in spring cloud gateway: webFilterExchange.getChain().filter(exchange); WebFilterChain.filter(ServerWebExchange)

Anyone know what has been missed in spring cloud gateway, that is causing the call through it to explicitly calling remote javascript?