tRPC failing on static pages (app router) build on Vercel

- info Collecting page data...
- info Generating static pages (0/4)
- info Generating static pages (1/4)
###################### URL https://***.vercel.app/api/trpc
###################### URL https://***.vercel.app/api/trpc
- info Generating static pages (2/4)
- info Generating static pages (3/4)
 << query  #1 travel.getCurrentTravel  {
  input: undefined,
  result: TRPCClientError: Unexpected token < in JSON at position 0
      at TRPCClientError.from (/vercel/path0/.next/server/chunks/41.js:26142:16)
      at /vercel/path0/.next/server/chunks/41.js:26293:36 {
    meta: { response: [Response] },
    shape: undefined,
    data: undefined,
    [cause]: SyntaxError: Unexpected token < in JSON at position 0
        at JSON.parse (<anonymous>)
        at parseJSONFromBytes (node:internal/deps/undici/undici:6571:19)
        at successSteps (node:internal/deps/undici/undici:6545:27)
        at node:internal/deps/undici/undici:1211:60
        at node:internal/process/task_queues:140:7
        at AsyncResource.runInAsyncScope (node:async_hooks:203:9)
        at AsyncResource.runMicrotask (node:internal/process/task_queues:137:8)
  },
  elapsedMs: 562
}