diff --git a/sdrgui/dsp/scopevis.cpp b/sdrgui/dsp/scopevis.cpp
index f5abef980..c64165386 100644
--- a/sdrgui/dsp/scopevis.cpp
+++ b/sdrgui/dsp/scopevis.cpp
@@ -229,19 +229,19 @@ void ScopeVis::feed(const SampleVector::const_iterator& cbegin, const SampleVect
     }
 
     if (m_freeRun) {
-        m_triggerPoint = cbegin;
+        m_triggerLocation = end - cbegin;
     }
     else if (m_triggerState == TriggerTriggered) {
-        m_triggerPoint = cbegin;
+        m_triggerLocation = end - cbegin;
     }
     else if (m_triggerState == TriggerUntriggered) {
-        m_triggerPoint = end;
+        m_triggerLocation = 0;
     }
     else if (m_triggerWaitForReset) {
-        m_triggerPoint = end;
+        m_triggerLocation = 0;
     }
     else {
-        m_triggerPoint = cbegin;
+        m_triggerLocation = end - cbegin;
     }
 
     SampleVector::const_iterator begin(cbegin);
@@ -254,7 +254,7 @@ void ScopeVis::feed(const SampleVector::const_iterator& cbegin, const SampleVect
             triggerPointToEnd = -1;
             processTrace(begin, end, triggerPointToEnd); // use all buffer
             if (triggerPointToEnd >= 0) {
-                m_triggerPoint = end - triggerPointToEnd;
+                m_triggerLocation = triggerPointToEnd;
             }
 
             begin = end; // effectively breaks out the loop
@@ -264,7 +264,8 @@ void ScopeVis::feed(const SampleVector::const_iterator& cbegin, const SampleVect
             triggerPointToEnd = -1;
             processTrace(begin, begin + m_traceSize, triggerPointToEnd); // use part of buffer to fit trace size
             if (triggerPointToEnd >= 0) {
-                m_triggerPoint = begin + m_traceSize -triggerPointToEnd;
+                //m_triggerPoint = begin + m_traceSize - triggerPointToEnd;
+                m_triggerLocation = triggerPointToEnd - m_traceSize;
             }
 
             begin += m_traceSize;
diff --git a/sdrgui/dsp/scopevis.h b/sdrgui/dsp/scopevis.h
index 34ff6a387..489fc27ac 100644
--- a/sdrgui/dsp/scopevis.h
+++ b/sdrgui/dsp/scopevis.h
@@ -243,7 +243,7 @@ public:
     virtual void start();
     virtual void stop();
     virtual bool handleMessage(const Message& message);
-    SampleVector::const_iterator getTriggerPoint() const { return m_triggerPoint; }
+    int getTriggerLocation() const { return m_triggerLocation; }
 
 private:
     // === messages ===
@@ -1132,7 +1132,7 @@ private:
     uint32_t m_timeBase;                           //!< Trace display time divisor
     uint32_t m_timeOfsProMill;                     //!< Start trace shift in 1/1000 trace size
     bool m_traceStart;                             //!< Trace is at start point
-    SampleVector::const_iterator m_triggerPoint;   //!< Trigger start location in the samples vector
+    int m_triggerLocation;                         //!< Trigger location from end point
     int m_sampleRate;                              //!< Actual sample rate being used
     int m_liveSampleRate;                          //!< Sample rate in live mode
     int m_liveLog2Decim;                           //!< Sample rate decimation log2 in live mode
diff --git a/sdrgui/dsp/spectrumscopecombovis.cpp b/sdrgui/dsp/spectrumscopecombovis.cpp
index 627be45a5..e7b6e2feb 100644
--- a/sdrgui/dsp/spectrumscopecombovis.cpp
+++ b/sdrgui/dsp/spectrumscopecombovis.cpp
@@ -18,8 +18,14 @@ void SpectrumScopeComboVis::feed(const SampleVector::const_iterator& begin, cons
 {
     (void) positiveOnly;
 	m_scopeVis->feed(begin, end, false);
-	SampleVector::const_iterator triggerPoint = m_scopeVis->getTriggerPoint();
-	m_spectrumVis->feedTriggered(triggerPoint, end, positiveOnly);
+	//SampleVector::const_iterator triggerPoint = m_scopeVis->getTriggerPoint();
+	//m_spectrumVis->feedTriggered(triggerPoint, end, positiveOnly);
+	int triggerPointLocation = m_scopeVis->getTriggerLocation();
+	if ((triggerPointLocation >= 0) && (triggerPointLocation < end - begin)) {
+	    m_spectrumVis->feedTriggered(end - triggerPointLocation, end, positiveOnly);
+	} else {
+	    m_spectrumVis->feedTriggered(begin, end, positiveOnly);
+	}
 }
 
 void SpectrumScopeComboVis::start()
diff --git a/sdrgui/dsp/spectrumvis.cpp b/sdrgui/dsp/spectrumvis.cpp
index 0fbeb0384..9f52ce9b3 100644
--- a/sdrgui/dsp/spectrumvis.cpp
+++ b/sdrgui/dsp/spectrumvis.cpp
@@ -78,11 +78,14 @@ void SpectrumVis::feed(const SampleVector::const_iterator& cbegin, const SampleV
 {
 	// if no visualisation is set, send the samples to /dev/null
 
-	if(m_glSpectrum == 0)
-	{
+	if (m_glSpectrum == 0) {
 		return;
 	}
 
+    if (!m_mutex.tryLock(0)) { // prevent conflicts with configuration process
+        return;
+    }
+
 	SampleVector::const_iterator begin(cbegin);
 
 	while (begin < end)
@@ -92,8 +95,6 @@ void SpectrumVis::feed(const SampleVector::const_iterator& cbegin, const SampleV
 
 		if (todo >= samplesNeeded)
 		{
-			QMutexLocker mutexLocker(&m_mutex);
-
 			// fill up the buffer
 			std::vector<Complex>::iterator it = m_fftBuffer.begin() + m_fftBufferFill;
 
@@ -296,6 +297,8 @@ void SpectrumVis::feed(const SampleVector::const_iterator& cbegin, const SampleV
 			m_needMoreSamples = true;
 		}
 	}
+
+	 m_mutex.unlock();
 }
 
 void SpectrumVis::start()