UMaterialInstanceDynamic::SetTextureParameterValue generate crash in the render thread

I was trying to make some cool shader stuff and then I ran into a huge problem:
in my Character::tick if I call
PostProcessColoration->SetTextureParameterValue(“ColorationData0”, mapPlane->getRenderTarget());
I get a beautiful crash with this callstack:



FGenericPlatformMisc::RaiseException(unsigned int) Address = 0x10b92e85b (filename not found) [in UE4Editor-Core.dylib]
FOutputDeviceMacError::Serialize(wchar_t const*, ELogVerbosity::Type, FName const&) Address = 0x10baeb7c2 (filename not found) [in UE4Editor-Core.dylib]
FOutputDevice::Logf(wchar_t const*, ...) Address = 0x10bb67207 (filename not found) [in UE4Editor-Core.dylib]
FDebug::AssertFailed(char const*, char const*, int, wchar_t const*, ...) Address = 0x10bb6295b (filename not found) [in UE4Editor-Core.dylib]
FUniformExpressionSet::CreateUniformBuffer(FMaterialRenderContext const&, FRHICommandList*, FLocalUniformBuffer*) const Address = 0x10e1c6a4a (filename not found) [in UE4Editor-Engine.dylib]
FMaterialRenderProxy::EvaluateUniformExpressions(FUniformExpressionCache&, FMaterialRenderContext const&, FRHICommandList*) const Address = 0x10e1c50f4 (filename not found) [in UE4Editor-Engine.dylib]
FMaterialRenderProxy::CacheUniformExpressions() Address = 0x10e1c790a (filename not found) [in UE4Editor-Engine.dylib]
TGraphTask<FMaterialRenderProxy::CacheUniformExpressions_GameThread()::EURCMacro_FCacheUniformExpressionsCommand>::ExecuteTask(TArray<FBaseGraphTask*, FDefaultAllocator>&, ENamedThreads::Type) Address = 0x10e254ad0 (filename not found) [in UE4Editor-Engine.dylib]
FNamedTaskThread::ProcessTasksNamedThread(int, bool) Address = 0x10b964f91 (filename not found) [in UE4Editor-Core.dylib]
FNamedTaskThread::ProcessTasksUntilQuit(int) Address = 0x10b960a35 (filename not found) [in UE4Editor-Core.dylib]
FTaskGraphImplementation::ProcessThreadUntilRequestReturn(ENamedThreads::Type) Address = 0x10b95d2d1 (filename not found) [in UE4Editor-Core.dylib]
RenderingThreadMain(FEvent*) Address = 0x112723364 (filename not found) [in UE4Editor-RenderCore.dylib]
FRenderingThread::Run() Address = 0x112735787 (filename not found) [in UE4Editor-RenderCore.dylib]
FRunnableThreadPThread::Run() Address = 0x10b9ae948 (filename not found) [in UE4Editor-Core.dylib]
FRunnableThreadPThread::_ThreadProc(void*) Address = 0x10b978661 (filename not found) [in UE4Editor-Core.dylib]
_pthread_body Address = 0x7fff8e9b1aab (filename not found) [in libsystem_pthread.dylib]
_pthread_body Address = 0x7fff8e9b19f7 (filename not found) [in libsystem_pthread.dylib]
thread_start Address = 0x7fff8e9b11fd (filename not found) [in libsystem_pthread.dylib]

As you can see my code does not appear in this log it’s only from the engine.
my “PostProcessColoration” object is okay I can call:
“PostProcessColoration->SetVectorParameterValue” without any problem. It’s specific to the “SetTextureParameterValue” call.
My mapPlane is not NULL. I get it using “UGameplayStatics::GetAllActorsOfClass” and it looks like this:

    AColourPlaneActor::AColourPlaneActor() {
        renderTarget = CreateDefaultSubobject<UTextureRenderTarget2D>(TEXT("RT"));
        renderTarget->InitAutoFormat(1024, 1024);
        renderTarget->OverrideFormat = EPixelFormat::PF_FloatRGB;
        renderTarget->ClearColor = FLinearColor( 1.f, 0.f, 0.f, 0.f );
        renderTarget->bNeedsTwoCopies = false;
        renderTarget->AddressX = TA_Wrap;
        renderTarget->AddressY = TA_Wrap;
        renderTarget->ClearColor = FLinearColor::Black;
    UTextureRenderTarget2D* AColourPlaneActor::getRenderTarget() {
        return renderTarget;

class HANA_API AColourPlaneActor : public AStaticMeshActor
    UPROPERTY(VisibleAnywhere, BlueprintReadOnly, Category=debug) UTextureRenderTarget2D* renderTarget;
    UTextureRenderTarget2D* getRenderTarget();

I can see my renderTarget in the Editor without any problem. I’m confused: my material is ok, my texture is ok and the crash does not appear in my code.
Is this a bug from the engine or from me ?
I’m on OSX using a MBP 2015 with an AMD R9370X.
thank you for your help.
PS: updating in 4.14 does not help…