Loosing Focus While Typing On Custom Input Field

I'm using custom component to show the text input field nothing fancy just the basic component

```
const CustomTextField = ({ ...rest }) => {
return ;
};
```
When I'm trying to using this component inside *react-final-form-array* for some reason I'm loosing the focus when typing on the input field, I guess its because of the re-rendering.

```
{
return (

);
}}
placeholder="Last Name"
/>
```

here is the link to the full code on [codesandbox](https://codesandbox.io/s/react-final-form-field-arrays-forked-gguhd?file=/index.js:1961-2313)

As you can see the "First Name" works fine but the "Last Name" loosing focus while typing.

How can I fix this issue, any help is appreciated

Thanks

Start with the linked CodeSandbox, specifically index.js, and compare the working First Name field with the Last Name field inside react-final-form-array. Reproduce the focus loss while typing and identify what differs; done means the Last Name input retains focus and accepts successive keystrokes.

Written by the indexing model from the issue text.