Here's a TS Playground:

import type { Jsonify } from "type-fest";

type Data = Jsonify<{
  payload: Record<string, any>;
}>;

declare const d: Data;
console.log(d.payload) // <-- Property 'payload' does not exist on type 'JsonifyObject<{}>'.

This feels like a bug to me. It's causing an issue for me in the upcoming version of Remix: remix-run/remix#7246

My current workaround is to change the type to unknown instead of any (edmundhung/conform#272 which will hopefully be merged soon). I think is the proper thing to do, but sometimes that's hard because you may not control the type. I think it's more correct to keep the record around on the type.