diff --git a/Source/Engine/Graphics/GPUBuffer.cpp b/Source/Engine/Graphics/GPUBuffer.cpp
index a38c88dd0..6aaa939b3 100644
--- a/Source/Engine/Graphics/GPUBuffer.cpp
+++ b/Source/Engine/Graphics/GPUBuffer.cpp
@@ -377,12 +377,9 @@ void GPUBuffer::SetData(const void* data, uint32 size)
         Log::ArgumentOutOfRangeException(TEXT("Buffer.SetData"));
         return;
     }
-
     void* mapped = Map(GPUResourceMapMode::Write);
     if (!mapped)
-    {
         return;
-    }
     Platform::MemoryCopy(mapped, data, size);
     Unmap();
 }
diff --git a/Source/Engine/Graphics/GPUBuffer.h b/Source/Engine/Graphics/GPUBuffer.h
index 8a5418570..4d14124b3 100644
--- a/Source/Engine/Graphics/GPUBuffer.h
+++ b/Source/Engine/Graphics/GPUBuffer.h
@@ -190,6 +190,7 @@ public:
     /// <summary>
     /// Gets a CPU pointer to the resource by mapping its contents. Denies the GPU access to that resource.
     /// </summary>
+    /// <remarks>Always call Unmap if the returned pointer is valid to release resources.</remarks>
     /// <param name="mode">The map operation mode.</param>
     /// <returns>The pointer of the mapped CPU buffer with resource data or null if failed.</returns>
     API_FUNCTION() virtual void* Map(GPUResourceMapMode mode) = 0;
diff --git a/Source/Engine/GraphicsDevice/DirectX/DX11/GPUBufferDX11.cpp b/Source/Engine/GraphicsDevice/DirectX/DX11/GPUBufferDX11.cpp
index 5c98bf579..b83ab6a08 100644
--- a/Source/Engine/GraphicsDevice/DirectX/DX11/GPUBufferDX11.cpp
+++ b/Source/Engine/GraphicsDevice/DirectX/DX11/GPUBufferDX11.cpp
@@ -48,18 +48,19 @@ void* GPUBufferDX11::Map(GPUResourceMapMode mode)
     const HRESULT result = _device->GetIM()->Map(_resource, 0, mapType, mapFlags, &map);
     if (result != DXGI_ERROR_WAS_STILL_DRAWING)
         LOG_DIRECTX_RESULT(result);
+
     _mapped = map.pData != nullptr;
+    if (!_mapped && !isMainThread)
+        _device->Locker.Unlock();
+
     return map.pData;
 }
 
 void GPUBufferDX11::Unmap()
 {
-    if (_mapped)
-    {
-        _mapped = false;
-        _device->GetIM()->Unmap(_resource, 0);
-    }
-    
+    ASSERT(_mapped);
+    _mapped = false;
+    _device->GetIM()->Unmap(_resource, 0);
     if (!IsInMainThread())
         _device->Locker.Unlock();
 }
diff --git a/Source/Engine/Particles/ParticlesSimulation.cpp b/Source/Engine/Particles/ParticlesSimulation.cpp
index 2d52a7f76..c68862925 100644
--- a/Source/Engine/Particles/ParticlesSimulation.cpp
+++ b/Source/Engine/Particles/ParticlesSimulation.cpp
@@ -104,15 +104,18 @@ int32 ParticleSystemInstance::GetParticlesCount() const
     if (GPUParticlesCountReadback && GPUParticlesCountReadback->IsAllocated())
     {
         auto data = static_cast<uint32*>(GPUParticlesCountReadback->Map(GPUResourceMapMode::Read));
-        for (const auto& emitter : Emitters)
+        if (data)
         {
-            if (emitter.Buffer && emitter.Buffer->Mode == ParticlesSimulationMode::GPU && emitter.Buffer->GPU.HasValidCount)
+            for (const auto& emitter : Emitters)
             {
-                result += *data;
+                if (emitter.Buffer && emitter.Buffer->Mode == ParticlesSimulationMode::GPU && emitter.Buffer->GPU.HasValidCount)
+                {
+                    result += *data;
+                }
+                ++data;
             }
-            ++data;
+            GPUParticlesCountReadback->Unmap();
         }
-        GPUParticlesCountReadback->Unmap();
     }
     else if (Emitters.HasItems())
     {
diff --git a/Source/Engine/Renderer/GI/GlobalSurfaceAtlasPass.cpp b/Source/Engine/Renderer/GI/GlobalSurfaceAtlasPass.cpp
index 5d87858b6..860c1b285 100644
--- a/Source/Engine/Renderer/GI/GlobalSurfaceAtlasPass.cpp
+++ b/Source/Engine/Renderer/GI/GlobalSurfaceAtlasPass.cpp
@@ -689,8 +689,8 @@ bool GlobalSurfaceAtlasPass::Render(RenderContext& renderContext, GPUContext* co
                         objectsBufferCapacity = counter;
                         notReady = false;
                     }
+                    _culledObjectsSizeBuffer->Unmap();
                 }
-                _culledObjectsSizeBuffer->Unmap();
 
                 // Allow to be ready if the buffer was already used
                 if (notReady && surfaceAtlasData.CulledObjectsBuffer && surfaceAtlasData.CulledObjectsBuffer->IsAllocated())
diff --git a/Source/Engine/ShadowsOfMordor/Builder.Charts.cpp b/Source/Engine/ShadowsOfMordor/Builder.Charts.cpp
index f6ecfca00..bd9974bc2 100644
--- a/Source/Engine/ShadowsOfMordor/Builder.Charts.cpp
+++ b/Source/Engine/ShadowsOfMordor/Builder.Charts.cpp
@@ -152,7 +152,7 @@ void ShadowsOfMordor::Builder::updateLightmaps()
         {
             auto texture = textures[textureIndex];
             GPUDevice::Instance->Locker.Unlock();
-            if (!texture || texture->WaitForLoaded())
+            if (texture == nullptr || texture->WaitForLoaded())
             {
                 LOG(Error, "Lightmap load failed.");
                 return;
diff --git a/Source/Engine/ShadowsOfMordor/Builder.cpp b/Source/Engine/ShadowsOfMordor/Builder.cpp
index ccf956d47..1ce6670d8 100644
--- a/Source/Engine/ShadowsOfMordor/Builder.cpp
+++ b/Source/Engine/ShadowsOfMordor/Builder.cpp
@@ -276,6 +276,7 @@ void ShadowsOfMordor::Builder::saveState()
             context->Flush();
             Platform::Sleep(10);
             void* mapped = lightmapDataStaging->Map(GPUResourceMapMode::Read);
+            ASSERT(mapped);
             stream->WriteInt32(lightmapDataSize);
             stream->WriteBytes(mapped, lightmapDataSize);
             lightmapDataStaging->Unmap();