title: "Operator called default onErrorDropped" on Mono timeout
body: <p>In my Production code, I am getting errors in my logs when a Mono times out.<br>
  I have managed to recreate these errors with the following code:</p>
  
  <pre><code>@Test
  public void testScheduler() {
      Mono&lt;String&gt; callableMethod1 = callableMethod();
      callableMethod1.block();
  
      Mono&lt;String&gt; callableMethod2 = callableMethod();
      callableMethod2.block();
  }
  
  private Mono&lt;String&gt; callableMethod() {
      return Mono.fromCallable(() -&gt; {
          Thread.sleep(60);
          return "Success";
      })
              .subscribeOn(Schedulers.elastic())
              .timeout(Duration.ofMillis(50))
              .onErrorResume(throwable -&gt; Mono.just("Timeout"));
  }
  </code></pre>
  
  <p>In the <code>Mono.fromCallable</code> I am making a blocking call using a third-party library. When this call times out, I get errors similar to </p>
  
  <pre><code>reactor.core.publisher.Operators - Operator called default onErrorDropped
  reactor.core.publisher.Operators - Scheduler worker in group main failed with an uncaught exception
  </code></pre>
  
  <p>These errors also seem to be intermittent, sometimes when I run the code provided I get no errors at all. However when I repeat the call in a loop of say 10, I consistently get them. </p>