Remix useFetcher and Conform producing strange behaviour

[jashiels99]

Firstly, according to the Conform documentation, I should use useActionData to set the lastResult property. This doesn't appear to work. The server-side validation isn't being picked up by the hook, even though it is picked up in the Network tab. So I tried this:
lastResult: fetcher.state === 'idle' ? fetcher.data : null.

This made more sense to me, and the server-side validation errors were now appearing. If I was to submit this form by clicking the submit button, this would all work just fine. However, when the form is submitted by pressing 'Return', it appears I get some sort of race condition (I think??). I have attached a screenshot.

Any help would be much appreciated I've been stuck on this for a while now 🙏