title: RxJava2 timer and combineLatest
body: <p>kind of new to RxJava2
  I'm having problems with <code>timer</code> and <code>combineLatest</code> e.g.:</p>
  
  <pre><code>Observable.combineLatest(
    Observable.timer(5, TimeUnit.SECONDS).map { TimedData(it) },
    locationDataSource.listen(),
    sensorDataSource.listen().
    Function3 { timedData, location, sensorEvent -&gt; Combined(timedData, location, sensorEvent) }
  ).subscribeOn(Schedulers.io()).observeOn(AndroidSchedulers.mainThread()).subscribe {
    Log.d(TAG, "Timer -&gt; " + it.timedData)
  }
  </code></pre>
  
  <p>What's happening is that  <code>timedData</code> is only being update once, then it never fires again, all the other observables are begin updated.
  I've found <a href="https://github.com/ReactiveX/RxJava/issues/1717" rel="nofollow noreferrer">https://github.com/ReactiveX/RxJava/issues/1717</a>  but it's from 2014, so I would think it's already solved.</p>
  
  <p>Is this still happening because of BackPressure?</p>