unfortunately that's an intranet site, therefore is not publicly exposed. However, I can tell you it is an Angular 4 SPA, counting approx. 100+ components, build w/ Webpack 2, supporting chunks lazy loading and service workers.
IMHO, I feel like some fetch calls, especially those used for prefetch, are causing the slowdown, but it could also be that some chunks are kind of heavy.
What I miss, in this sense, is an understanding of how TestCafé "proxies" calls/scripts and whether it may have some kind of middleware that struggles to deal with our amount of content.