diff --git a/source/Lib/CommonLib/Picture.cpp b/source/Lib/CommonLib/Picture.cpp
index 31c7f2cd4a2571d51d2aed6fa312d46d4542ce95..6af4fea11fe7113cd671f836bdd1a236ba665d9f 100644
--- a/source/Lib/CommonLib/Picture.cpp
+++ b/source/Lib/CommonLib/Picture.cpp
@@ -201,6 +201,7 @@ Picture::Picture()
   numSubpics = 1;
 #endif
   numSlices = 1;
+  unscaledPic = nullptr;
 }
 
 void Picture::create( const ChromaFormat &_chromaFormat, const Size &size, const unsigned _maxCUSize, const unsigned _margin, const bool _decoder, const int _layerId )
@@ -218,7 +219,6 @@ void Picture::create( const ChromaFormat &_chromaFormat, const Size &size, const
     M_BUFS( 0, PIC_TRUE_ORIGINAL ). create( _chromaFormat, a );
   }
 #if !KEEP_PRED_AND_RESI_SIGNALS
-
   m_ctuArea = UnitArea( _chromaFormat, Area( Position{ 0, 0 }, Size( _maxCUSize, _maxCUSize ) ) );
 #endif
   m_hashMap.clearAll();
diff --git a/source/Lib/CommonLib/Slice.cpp b/source/Lib/CommonLib/Slice.cpp
index 680dd56b59c0177429334f8268f876d97bc4fce7..fcfe7a40dfca3be7372df24678d88bf910126782 100644
--- a/source/Lib/CommonLib/Slice.cpp
+++ b/source/Lib/CommonLib/Slice.cpp
@@ -4296,6 +4296,8 @@ void Slice::scaleRefPicList( Picture *scaledRefPic[ ], PicHeader *picHeader, APS
       CU::getRprScaling( sps, pps, m_apcRefPicList[refList][rIdx], xScale, yScale );
       m_scalingRatio[refList][rIdx] = std::pair<int, int>( xScale, yScale );
 
+      CHECK( m_apcRefPicList[refList][rIdx]->unscaledPic == nullptr, "unscaledPic is not properly set" );
+
       if( m_apcRefPicList[refList][rIdx]->isRefScaled( pps ) == false )
       {
         refPicIsSameRes = true;
diff --git a/source/Lib/DecoderLib/DecLib.cpp b/source/Lib/DecoderLib/DecLib.cpp
index 1666209fb97c0b499e0eb581aed3feebc4512f86..ac9d073c34354e00df7afe5f6611782e80cea21a 100644
--- a/source/Lib/DecoderLib/DecLib.cpp
+++ b/source/Lib/DecoderLib/DecLib.cpp
@@ -2356,7 +2356,6 @@ bool DecLib::xDecodeSlice(InputNALUnit &nalu, int &iSkipFrame, int iPOCLastDispl
   pcSlice->setPrevGDRSubpicPOC(m_prevGDRSubpicPOC[nalu.m_nuhLayerId][currSubPicIdx]);
   pcSlice->setPrevIRAPSubpicPOC(m_prevIRAPSubpicPOC[nalu.m_nuhLayerId][currSubPicIdx]);
   pcSlice->setPrevIRAPSubpicType(m_prevIRAPSubpicType[nalu.m_nuhLayerId][currSubPicIdx]);
-  pcSlice->setPrevIRAPSubpicType(m_prevIRAPSubpicType[nalu.m_nuhLayerId][currSubPicIdx]);
   pcSlice->checkSubpicTypeConstraints(m_cListPic, pcSlice->getRPL0(), pcSlice->getRPL1(), m_prevIRAPSubpicDecOrderNo[nalu.m_nuhLayerId][currSubPicIdx]);
   pcSlice->checkRPL(pcSlice->getRPL0(), pcSlice->getRPL1(), m_associatedIRAPDecodingOrderNumber[nalu.m_nuhLayerId], m_cListPic);
   pcSlice->checkSTSA(m_cListPic);
diff --git a/source/Lib/EncoderLib/EncGOP.cpp b/source/Lib/EncoderLib/EncGOP.cpp
index e0feb2869b3f4f557cdc7c88bebedf229837baca..8a6031806a0d76596bd678aa9404dcda96b4e597 100644
--- a/source/Lib/EncoderLib/EncGOP.cpp
+++ b/source/Lib/EncoderLib/EncGOP.cpp
@@ -2495,6 +2495,8 @@ void EncGOP::compressGOP( int iPOCLast, int iNumPicRcvd, PicList& rcListPic,
 
       for( int refIdx = 0; refIdx < pcSlice->getNumRefIdx( REF_PIC_LIST_0 ); refIdx++ )
       {
+        CHECK( pcSlice->getRefPic( REF_PIC_LIST_0, refIdx )->unscaledPic == nullptr, "unscaledPic is not set for L0 reference picture" );
+
         if( pcSlice->getRefPic( REF_PIC_LIST_0, refIdx )->isRefScaled( pcSlice->getPPS() ) == false )
         {
           colRefIdxL0 = refIdx;
@@ -2506,6 +2508,8 @@ void EncGOP::compressGOP( int iPOCLast, int iNumPicRcvd, PicList& rcListPic,
       {
         for( int refIdx = 0; refIdx < pcSlice->getNumRefIdx( REF_PIC_LIST_1 ); refIdx++ )
         {
+          CHECK( pcSlice->getRefPic( REF_PIC_LIST_1, refIdx )->unscaledPic == nullptr, "unscaledPic is not set for L1 reference picture" );
+
           if( pcSlice->getRefPic( REF_PIC_LIST_1, refIdx )->isRefScaled( pcSlice->getPPS() ) == false )
           {
             colRefIdxL1 = refIdx;
@@ -2528,6 +2532,9 @@ void EncGOP::compressGOP( int iPOCLast, int iNumPicRcvd, PicList& rcListPic,
           refPicL1 = refPicL1->unscaledPic;
         }
 
+        CHECK( !refPicL0->slices.size(), "Wrong L0 reference picture" );
+        CHECK( !refPicL1->slices.size(), "Wrong L1 reference picture" );
+
         const uint32_t uiColFromL0 = refPicL0->slices[0]->getSliceQp() > refPicL1->slices[0]->getSliceQp();
         picHeader->setPicColFromL0Flag( uiColFromL0 );
         pcSlice->setColFromL0Flag( uiColFromL0 );