When your client-side app hydrates the server head tags, it will attempt to hydrate each element based on the nodes being equal $el.isEqualNode($newEl) or them sharing the same dedupe key (see Tag Deduping).

If you're rendering content that differs between client and server, you should specify a key attribute if the element does not have a unique dedupe key.

useHead({
  script: [
    {
      // key is needed to avoid seperate scripts being created
      key: 'my-script',
      innerHTML: process.server ? '' : 'console.log("hello world")',
    }
  ]
})