Can't get better-auth working with the Tanstack Start and Convex stack

The weird part is the error gives me to nothing to work with, just fetch failed and even weirder is that it wouldn't happen on every reload, but when the page does reload, client interactivity wouldn't work, meaning no onClick handler stuff is working. Neither server nor browser console tells me anything. Have followed, checked and rechecked the setup process. https://convex-better-auth.netlify.app/framework-guides/tanstack-start

TanStack Start | Convex + Better Auth

Install and configure Convex + Better Auth for TanStack Start.