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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

instance.componentWillUnmount();
  stopPhaseTimer();
};
// Capture errors so they don't interrupt unmounting.
function safelyCallComponentWillUnmount(current, instance) {
  if (__DEV__) {
    invokeGuardedCallback(
      null,
      callComponentWillUnmountWithTimer,
      null,
      current,
      instance,
    );
    if (hasCaughtError()) {
      const unmountError = clearCaughtError();
      captureCommitPhaseError(current, unmountError);
    }
  } else {
    try {
      callComponentWillUnmountWithTimer(current, instance);
    } catch (unmountError) {
      captureCommitPhaseError(current, unmountError);
    }
  }
}
function safelyDetachRef(current: Fiber) {
  const ref = current.ref;
  if (ref !== null) {
    if (typeof ref === 'function') {
      if (__DEV__) {