diff --git a/src/demod.hh b/src/demod.hh
index 54f7c9f..2bd14b4 100644
--- a/src/demod.hh
+++ b/src/demod.hh
@@ -44,7 +44,7 @@ public:
     _buffer =  Buffer<Scalar>(src_cfg.bufferSize());
 
     LogMessage msg(LOG_DEBUG);
-    msg << "Configure AMDemod:" << std::endl
+    msg << "Configure AMDemod: " << this << std::endl
         << " input type: " << Traits< std::complex<Scalar> >::scalarId << std::endl
         << " output type: " << Traits<Scalar>::scalarId << std::endl
         << " sample rate: " << src_cfg.sampleRate() << std::endl
@@ -128,7 +128,7 @@ public:
     _buffer =  Buffer<Scalar>(src_cfg.bufferSize());
 
     LogMessage msg(LOG_DEBUG);
-    msg << "Configure USBDemod:" << std::endl
+    msg << "Configure USBDemod: " << this << std::endl
         << " input type: " << Traits< std::complex<Scalar> >::scalarId << std::endl
         << " output type: " << Traits<Scalar>::scalarId << std::endl
         << " sample rate: " << src_cfg.sampleRate() << std::endl
@@ -216,7 +216,7 @@ public:
     _can_overwrite = (sizeof(std::complex<iScalar>) >= sizeof(oScalar));
 
     LogMessage msg(LOG_DEBUG);
-    msg << "Configured FMDemod node:" << std::endl
+    msg << "Configured FMDemod node: " << this << std::endl
         << " sample-rate: " << src_cfg.sampleRate() << std::endl
         << " in-type / out-type: " << src_cfg.type()
         << " / " << Config::typeId<oScalar>() << std::endl
diff --git a/src/gui/waterfallview.cc b/src/gui/waterfallview.cc
index a2e2ed2..c39ba35 100644
--- a/src/gui/waterfallview.cc
+++ b/src/gui/waterfallview.cc
@@ -102,6 +102,7 @@ WaterFallView::_onSpectrumUpdated() {
   for (size_t i=0; i<_N; i++) {
     int idx = (_spectrum->fftSize()/2+i) % _spectrum->fftSize();
     double value = 10*log10(_spectrum->spectrum()[idx])-10*log10(_N);
+    if (value != value) { value = 0; }
     painter.setPen((*_colorMap)(value));
     painter.drawPoint(i, _M-1);
   }
diff --git a/src/node.cc b/src/node.cc
index 8357e22..eb63fae 100644
--- a/src/node.cc
+++ b/src/node.cc
@@ -73,10 +73,11 @@ Source::send(const RawBuffer &buffer, bool allow_overwrite) {
       // iff, the sink is the only one receiving this buffer, the source allows it and the
       // connection is direct.
       allow_overwrite = allow_overwrite && (1 == _sinks.size());
+      // Call sink directly
       item->first->handleBuffer(buffer, allow_overwrite);
     }
-    // otherwise, queue buffer
     else {
+      // otherwise, queue buffer
       allow_overwrite = allow_overwrite && (1 == _sinks.size());
       Queue::get().send(buffer, item->first, allow_overwrite);
     }
diff --git a/src/queue.cc b/src/queue.cc
index 00249bd..171233c 100644
--- a/src/queue.cc
+++ b/src/queue.cc
@@ -68,8 +68,15 @@ Queue::stop() {
 
 void
 Queue::wait() {
-  void *p;
-  pthread_join(_thread, &p);
+  // Wait for the queue to quit
+  void *p; pthread_join(_thread, &p);
+
+  // Clear queue.
+  std::list<Message>::iterator item = _queue.begin();
+  for (; item != _queue.end(); item++) {
+    item->buffer().unref();
+  }
+  _queue.clear();
 }
 
 
@@ -110,7 +117,11 @@ Queue::_main()
   }
   // Call all stop-signal handlers
   _signalStop();
-  Logger::get().log(LogMessage(LOG_DEBUG, "Queue stopped."));
+  {
+    LogMessage msg(LOG_DEBUG, "Queue stopped.");
+    msg << " Messages left in queue: " << _queue.size();
+    Logger::get().log(msg);
+  }
 }
 
 void
diff --git a/src/rtlsource.cc b/src/rtlsource.cc
index 2473b20..b1bdbcb 100644
--- a/src/rtlsource.cc
+++ b/src/rtlsource.cc
@@ -80,8 +80,11 @@ RTLSource::setSampleRate(double sample_rate) {
   if (sr < 225001) { sr = 225001; }
   else if ((sr>300000) && (sr<900001)) { sr = 900001; }
   else if (sr>2400000) { sr = 2400000; }
+
   rtlsdr_set_sample_rate(_device, sr);
+  rtlsdr_reset_buffer(_device);
   _sample_rate = rtlsdr_get_sample_rate(_device);
+
   this->setConfig(Config(Config::Type_cu8, _sample_rate, _buffer_size, 15));
 }
 
@@ -110,7 +113,9 @@ RTLSource::stop() {
   void *p;
   // stop async reading of RTL device
   rtlsdr_cancel_async(_device);
-  // Wait for blocked thread to exit
+  // Wait for blocked thread to exit:
+  //  This is important to ensure that no new messages are added to the
+  //  queue after this function returned.
   pthread_join(_thread, &p);
 }