diff --git a/src/waveform/vsyncthread.cpp b/src/waveform/vsyncthread.cpp
index 9b8ec2e1af9..08c0bfbfad3 100644
--- a/src/waveform/vsyncthread.cpp
+++ b/src/waveform/vsyncthread.cpp
@@ -24,7 +24,7 @@ VSyncThread::VSyncThread(QObject* pParent)
 
 VSyncThread::~VSyncThread() {
     m_bDoRendering = false;
-    m_semaVsyncSlot.release(2); // Two slots
+    m_semaVsyncSlot.release(m_vSyncMode == ST_PLL ? 1 : 2); // Two slots, one for PLL
     wait();
     //delete m_glw;
 }
@@ -95,7 +95,6 @@ void VSyncThread::run() {
             // and render them for the next swap
             emit vsyncSwapAndRender();
             m_semaVsyncSlot.acquire();
-            m_semaVsyncSlot.acquire();
             if (m_sinceLastSwap.toIntegerMicros() > sleepForSkippedFrames + pllDeltaOut * 3 / 2) {
                 m_droppedFrames++;
                 // Adjusting the offset on each frame drop ends up at
diff --git a/src/waveform/waveformwidgetfactory.cpp b/src/waveform/waveformwidgetfactory.cpp
index f61198e43f0..17212b2f0db 100644
--- a/src/waveform/waveformwidgetfactory.cpp
+++ b/src/waveform/waveformwidgetfactory.cpp
@@ -687,7 +687,7 @@ void WaveformWidgetFactory::notifyZoomChange(WWaveformViewer* viewer) {
     }
 }
 
-void WaveformWidgetFactory::render() {
+void WaveformWidgetFactory::renderSelf() {
     ScopedTimer t("WaveformWidgetFactory::render() %1waveforms",
             static_cast<int>(m_waveformWidgetHolders.size()));
 
@@ -759,10 +759,14 @@ void WaveformWidgetFactory::render() {
     m_pGuiTick->process();
 
     //qDebug() << "refresh end" << m_vsyncThread->elapsed();
+}
+
+void WaveformWidgetFactory::render() {
+    renderSelf();
     m_vsyncThread->vsyncSlotFinished();
 }
 
-void WaveformWidgetFactory::swap() {
+void WaveformWidgetFactory::swapSelf() {
     ScopedTimer t("WaveformWidgetFactory::swap() %1waveforms",
             static_cast<int>(m_waveformWidgetHolders.size()));
 
@@ -797,13 +801,17 @@ void WaveformWidgetFactory::swap() {
         // If we are using WVuMeter, this does nothing
         emit swapVuMeters();
     }
-    //qDebug() << "swap end" << m_vsyncThread->elapsed();
+}
+
+void WaveformWidgetFactory::swap() {
+    swapSelf();
     m_vsyncThread->vsyncSlotFinished();
 }
 
 void WaveformWidgetFactory::swapAndRender() {
-    swap();
-    render();
+    swapSelf();
+    renderSelf();
+    m_vsyncThread->vsyncSlotFinished();
 }
 
 void WaveformWidgetFactory::slotFrameSwapped() {
diff --git a/src/waveform/waveformwidgetfactory.h b/src/waveform/waveformwidgetfactory.h
index 8c4761eb893..17054366918 100644
--- a/src/waveform/waveformwidgetfactory.h
+++ b/src/waveform/waveformwidgetfactory.h
@@ -162,6 +162,9 @@ class WaveformWidgetFactory : public QObject, public Singleton<WaveformWidgetFac
     void slotFrameSwapped();
 
   private:
+    void renderSelf();
+    void swapSelf();
+
     void evaluateWidgets();
     template<typename WaveformT>
     QString buildWidgetDisplayName() const;