diff --git a/Gems/SceneProcessing/Code/Source/Generation/Components/MeshOptimizer/MeshBuilderSkinningInfo.h b/Gems/SceneProcessing/Code/Source/Generation/Components/MeshOptimizer/MeshBuilderSkinningInfo.h
index f5b716876e..dd3b715a21 100644
--- a/Gems/SceneProcessing/Code/Source/Generation/Components/MeshOptimizer/MeshBuilderSkinningInfo.h
+++ b/Gems/SceneProcessing/Code/Source/Generation/Components/MeshOptimizer/MeshBuilderSkinningInfo.h
@@ -35,7 +35,7 @@ namespace AZ::MeshBuilder
 
         MeshBuilderSkinningInfo(size_t numOrgVertices);
 
-        void AddInfluence(size_t orgVtxNr, const Influence& influence)             { mInfluences.resize(AZStd::max(mInfluences.size(), orgVtxNr)); mInfluences.at(orgVtxNr).emplace_back(influence); }
+        void AddInfluence(size_t orgVtxNr, const Influence& influence)             { mInfluences.resize(AZStd::max(mInfluences.size(), orgVtxNr + 1)); mInfluences.at(orgVtxNr).emplace_back(influence); }
         void RemoveInfluence(size_t orgVtxNr, size_t influenceNr)                  { mInfluences.at(orgVtxNr).erase(mInfluences.at(orgVtxNr).begin() + influenceNr); }
         const Influence& GetInfluence(size_t orgVtxNr, size_t influenceNr) const   { return mInfluences.at(orgVtxNr).at(influenceNr); }
         size_t GetNumInfluences(size_t orgVtxNr) const                             { return mInfluences.at(orgVtxNr).size(); }
diff --git a/Gems/SceneProcessing/Code/Source/Generation/Components/MeshOptimizer/MeshOptimizerComponent.cpp b/Gems/SceneProcessing/Code/Source/Generation/Components/MeshOptimizer/MeshOptimizerComponent.cpp
index 35d6db6d03..6bc47476f8 100644
--- a/Gems/SceneProcessing/Code/Source/Generation/Components/MeshOptimizer/MeshOptimizerComponent.cpp
+++ b/Gems/SceneProcessing/Code/Source/Generation/Components/MeshOptimizer/MeshOptimizerComponent.cpp
@@ -105,7 +105,6 @@ namespace AZ::SceneGenerationComponents
     // Vector3 as a key into a unordered_map.
     template <class MeshDataType>
     class Vector3Map
-        : private AZStd::unordered_map<AZ::Vector3, AZ::u32>
     {
     public:
         Vector3Map(const MeshDataType* meshData, bool hasBlendShapes, float positionTolerance)
@@ -116,9 +115,6 @@ namespace AZ::SceneGenerationComponents
         {
         }
 
-        using AZStd::unordered_map<AZ::Vector3, AZ::u32>::reserve;
-        using AZStd::unordered_map<AZ::Vector3, AZ::u32>::size;
-
         AZ::u32 operator[](const AZ::u32 vertexIndex)
         {
             if (m_hasBlendShapes)
@@ -130,7 +126,7 @@ namespace AZ::SceneGenerationComponents
                 return m_meshData->GetUsedPointIndexForControlPoint(m_meshData->GetControlPointIndex(vertexIndex));
             }
 
-            const auto& [iter, didInsert] = try_emplace(GetPositionForIndex(vertexIndex), m_currentOriginalVertexIndex);
+            const auto& [iter, didInsert] = m_map.try_emplace(GetPositionForIndex(vertexIndex), m_currentOriginalVertexIndex);
             if (didInsert)
             {
                 ++m_currentOriginalVertexIndex;
@@ -149,11 +145,32 @@ namespace AZ::SceneGenerationComponents
                 return m_meshData->GetUsedPointIndexForControlPoint(m_meshData->GetControlPointIndex(vertexIndex));
             }
 
-            auto iter = find(GetPositionForIndex(vertexIndex));
-            AZSTD_CONTAINER_ASSERT(iter != end(), "Element with key is not present");
+            auto iter = m_map.find(GetPositionForIndex(vertexIndex));
+            AZSTD_CONTAINER_ASSERT(iter != m_map.end(), "Element with key is not present");
             return iter->second;
         }
 
+        [[nodiscard]] size_t size() const
+        {
+            if (m_hasBlendShapes)
+            {
+                // Since blend shapes are present, the vertex welding is disabled, and the map will always be empty.
+                // Use the underlying mesh's vertex count instead.
+                return m_meshData->GetUsedControlPointCount();
+            }
+            return m_map.size();
+        }
+
+        void reserve(size_t count)
+        {
+            if (m_hasBlendShapes)
+            {
+                // Since blend shapes are present, the vertex welding is disabled, and the map will always be empty.
+                return;
+            }
+            m_map.reserve(count);
+        }
+
     private:
 
         AZ::Vector3 GetPositionForIndex(const AZ::u32 vertexIndex) const
@@ -167,6 +184,7 @@ namespace AZ::SceneGenerationComponents
             ) * m_positionTolerance;
         }
 
+        AZStd::unordered_map<AZ::Vector3, AZ::u32> m_map;
         const MeshDataType* m_meshData;
         bool m_hasBlendShapes;
         float m_positionTolerance;