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**Do you want to request a *feature* or report a *bug*?**
bug, I believe, unless I misunderstand how it works
**What is the current behavior?**
Given a `Suspense` inside `Suspense` case like
```
<Suspense fallback="Fallback 1">
  <LazyText1 text="First text" />
  <Suspense fallback="Fallback 2">
    <LazyText2 text="Second text!" />
  </Suspense>
</Suspense>
```

Promises in `LazyTexts` start resolving at the same time, but if `LazyText2` is resolved first it never renders, `Fallback 2` stays.

Result:
```
First text

Fallback 2
```

Please see https://codesandbox.io/s/234o4zry7n

**What is the expected behavior?**

Every `LazyText` displayed in the end
```
First text

Second text!
```

**Which versions of React, and which browser / OS are affected by this issue? Did this work in previous versions of React?**
react, react-dom 16.6.0

advanceTimeBy = amount => {
    currentTime += amount;
  };
  AdvanceTime = class extends React.Component {
    static defaultProps = {
      byAmount: 10,
      shouldComponentUpdate: true,
    };
    shouldComponentUpdate(nextProps) {
      return nextProps.shouldComponentUpdate;
    }
    render() {
      
      advanceTimeBy(this.props.byAmount);
      return this.props.children || null;
    }
  };
  resourcePromise = null;
  function yieldForRenderer(value) {
    if (ReactNoop) {
      ReactNoop.yield(value);
    } else {
      ReactTestRenderer.unstable_yield(value);
    }
  }
  TextResource = ReactCache.unstable_createResource(([text, ms = 0]) => {
    resourcePromise = new Promise((resolve, reject) =>
      setTimeout(() => {
        yieldForRenderer(`Promise resolved [${text}]`);
        resolve(text);