Problem when CSS missing and wayback option turned on

Problem accessing web page at firstdirect.com

Description of problem
When you click on the on line banking link, you get a page with a timer icon and nothing else and it just sits there forever.

Expected result
It should present a page asking for log in credentials. (It works in Firefox and Chrome)

How to reproduce
Got to the above URL and click on the online banking link at the top right of the page

Research results
Opening dev tools i see a strict mimetype checking error per this log:

    (index):1 Refused to apply style from 'https://www2.firstdirect.com/etc/designs/fsdt/online/app.1.13.0.28d595.css' because its MIME type ('text/html') is not a supported stylesheet MIME type, and strict MIME checking is enabled.
(index):112 GET https://www2.firstdirect.com/etc/designs/fsdt/online/vendor.0889c8.js net::ERR_ABORTED 404 (Not Found)
(index):113 GET https://www2.firstdirect.com/etc/designs/fsdt/online/app.1.13.0.28d595.js net::ERR_ABORTED 404 (Not Found)
(index):1 Refused to apply style from 'https://www2.firstdirect.com/etc/designs/fsdt/online/app.1.13.0.28d595.css' because its MIME type ('text/html') is not a supported stylesheet MIME type, and strict MIME checking is enabled.
(index):113 GET https://www2.firstdirect.com/etc/designs/fsdt/online/app.1.13.0.28d595.js net::ERR_ABORTED 404 (Not Found)

So I try to access https://www2.firstdirect.com/etc/designs/fsdt/online/vendor.0889c8.js directly and get 404 error and option to refer to wayback machine. I try this also in: Firefox (browser page is blank, but dev tools reprot 404) and Chrome (actually retrieves the file).

I suspect that " its MIME type (‘text/html’) is not a supported stylesheet MIME type, and strict MIME checking is enabled." is being triggered because the type checker code is testing the wayback machine message and finding it is text/html.

So I turn off the wayback machine option for 404 pages in Brave settings. Now the first direct page loads ok (it seems to be looking for a different style sheet page now)

It looks as though Brave is generating the wayback option screen, then checking the mimetype of that (which by now is presumably text/html) and getting upset that a stylesheet link is not text/css.

SUGGESTED FIX
EITHER Brave should not attempt to offer the wayback on css files OR should check the mimetype BEFORE substituting the wayback option web page.

Brave Version( check About Brave):
Version 1.14.81 Chromium: 85.0.4183.102 (Official Build) (64-bit)

Additional Information: