OnChange leads to "ghost data" appearing in field

[abrad45]

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?

<OnChange /> should work the same as the useEffect hook I commented out in the file. if you use that instead of <OnChange />, 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