title: Expo with create-react-native-app; inconsistent behaviour
body: <p>I work on a project started through CRNA (create-react-native-app) and I usually do </p>
  
  <ol>
  <li>yarn start</li>
  <li>Open project on Expo XDE</li>
  <li>Device > Open on Android (which starts it in my Android simulator (NoxPlayer)</li>
  </ol>
  
  <p>However, since 2 days ago, it's been on the "Building JavaScript bundle..." and is EXTREMELY slow (we're talking 2-3 hrs) before it just stagnates and stops progressing. (I tried rolling back to old branches that worked and the same problem was present.)</p>
  
  <p>I tried started a new clean slate project... Sometimes it works perfectly, sometimes it has the same slow build problem, sometimes it simply won't connect to the tunnel; an inconsistent behaviour.</p>
  
  <p>Any ideas on how to debug this or any similar alternative to Expo?</p>