title: React hook form - Register field not working
body: <p>here is my <a href="https://codesandbox.io/s/react-hook-form-unregister-v6-forked-19446?file=/src/index.js" rel="nofollow noreferrer">codesandbox</a>, I'm manually registering two fields, if I click submit w/o entering any data I see required field validation, which works fine and if I unregister &quot;lastname&quot; it removes error from last name, however,</p>
  <p>The problem: first name still shows required validation even if I enter data.
  I tried removing manual registering a field and it work fine. But that is not my requirement.
  Any help. Thank you.</p>