title: amplify - deployment not triggering after new merge
body: <p>I've set-up a <code>main</code> branch in Amplify frontend.<br/>
  Every time I have made changes on main branch, it should auto deploy a new version of frontend.<br/></p>
  <p>Everything works fine until today.<br/>
  After I've merged <code>dev</code> branch to <code>main</code> branch in Github, I go to Amplify and find that the pineline is not running</p>
  <p>It shows</p>
  <pre><code>Last commit: Merge pull request #230
  </code></pre>
  <p>But the latest one should be <code>#232</code></p>
  <p>How do I fix/debug it??</p>