OnChange leads to "ghost data" appearing in field

### Are you submitting a **bug report** or a **feature request**?

Bug Report

### What is the current behavior?

I have a field, `a`. Depending on the value of `a`, another field, `b`, appears. Additionally, when changing `a`, we need to change the value of `b` as well (either setting it or clearing it out). It's possible to get the value of `b` to read one thing, even though its value in the form state is something else. When you focus field `b` it snaps to that other value, seemingly indicating that it didn't rerender after its value changed (?)


### What is the expected behavior?

`` should work the same as the `useEffect` hook I commented out in the file. if you use that instead of ``, it works as I'd expect: the data in the form values should match the data reflected in the form field itself.

### Sandbox Link

https://codesandbox.io/s/ecstatic-kare-2jcts?file=/target.js

### What's your environment?

See sandbox: newest everything