During edit (not even PIE) turning on and off the ocean plane can cause a crash intermittently.
This may be limited to macOS.
Will further investigate, but just though I would dump in here for record.
FPlanarReflectionParameters::SetParameters(FRHICommandList&, FRHIPixelShader*, FSceneView const&, FPlanarReflectionSceneProxy const*) Address = 0x11a818e15 (filename not found) [in UE4Editor-Renderer.dylib]
FBasePassReflectionParameters::SetMesh(FRHICommandList&, FRHIPixelShader*, FSceneView const&, FPrimitiveSceneProxy const*, ERHIFeatureLevel::Type) Address = 0x11a48dafb (filename not found) [in UE4Editor-Renderer.dylib]
TBasePassDrawingPolicy<FUniformLightMapPolicy>::SetMeshRenderState(FRHICommandList&, FViewInfo const&, FPrimitiveSceneProxy const*, FMeshBatch const&, int, FDrawingPolicyRenderState&, TBasePassDrawingPolicy<FUniformLightMapPolicy>::ElementDataType const&, FMeshDrawingPolicy::ContextDataType) const Address = 0x11a5265f4 (filename not found) [in UE4Editor-Renderer.dylib]
int TStaticMeshDrawList<TBasePassDrawingPolicy<FUniformLightMapPolicy> >::DrawElement<(InstancedStereoPolicy)2>(FRHICommandList&, FViewInfo const&, FMeshDrawingPolicy::ContextDataType, FDrawingPolicyRenderState&, TStaticMeshDrawList<TBasePassDrawingPolicy<FUniformLightMapPolicy> >::FElement const&, unsigned long long, TStaticMeshDrawList<TBasePassDrawingPolicy<FUniformLightMapPolicy> >::FDrawingPolicyLink*, bool&) Address = 0x11a528315 (filename not found) [in UE4Editor-Renderer.dylib]
bool TStaticMeshDrawList<TBasePassDrawingPolicy<FUniformLightMapPolicy> >::DrawVisibleInner<(InstancedStereoPolicy)2>(FRHICommandList&, FViewInfo const&, FMeshDrawingPolicy::ContextDataType, FDrawingPolicyRenderState&, TBitArray<SceneRenderingBitArrayAllocator> const*, TArray<unsigned long long, TMemStackAllocator<0u> > const*, StereoPair const*, int, int, bool) Address = 0x11a527de6 (filename not found) [in UE4Editor-Renderer.dylib]
FDeferredShadingSceneRenderer::RenderBasePassStaticDataType(FRHICommandList&, FViewInfo&, FDrawingPolicyRenderState const&, EBasePassDrawListType) Address = 0x11a495b1d (filename not found) [in UE4Editor-Renderer.dylib]
FDeferredShadingSceneRenderer::RenderBasePassStaticData(FRHICommandList&, FViewInfo&, FDrawingPolicyRenderState const&) Address = 0x11a498aae (filename not found) [in UE4Editor-Renderer.dylib]
FDeferredShadingSceneRenderer::RenderBasePassView(FRHICommandListImmediate&, FViewInfo&, FExclusiveDepthStencil::Type) Address = 0x11a49586a (filename not found) [in UE4Editor-Renderer.dylib]
FDeferredShadingSceneRenderer::RenderBasePass(FRHICommandListImmediate&, FExclusiveDepthStencil::Type) Address = 0x11a494e28 (filename not found) [in UE4Editor-Renderer.dylib]
FDeferredShadingSceneRenderer::Render(FRHICommandListImmediate&) Address = 0x11a5895de (filename not found) [in UE4Editor-Renderer.dylib]
RenderViewFamily_RenderThread(FRHICommandListImmediate&, FSceneRenderer*) Address = 0x11add44e8 (filename not found) [in UE4Editor-Renderer.dylib]
TGraphTask<FRendererModule::BeginRenderingViewFamily(FCanvas*, FSceneViewFamily*)::EURCMacro_FDrawSceneCommand>::ExecuteTask(TArray<FBaseGraphTask*, FDefaultAllocator>&, ENamedThreads::Type) Address = 0x11adf5e3e (filename not found) [in UE4Editor-Renderer.dylib]
FNamedTaskThread::ProcessTasksNamedThread(int, bool) Address = 0x10a9d7b82 (filename not found) [in UE4Editor-Core.dylib]
FNamedTaskThread::ProcessTasksUntilQuit(int) Address = 0x10a9d63a8 (filename not found) [in UE4Editor-Core.dylib]
FTaskGraphImplementation::ProcessThreadUntilRequestReturn(ENamedThreads::Type) Address = 0x10a9d24ee (filename not found) [in UE4Editor-Core.dylib]
RenderingThreadMain(FEvent*) Address = 0x1107dd655 (filename not found) [in UE4Editor-RenderCore.dylib]
FRenderingThread::Run() Address = 0x1107f38d7 (filename not found) [in UE4Editor-RenderCore.dylib]
FRunnableThreadPThread::Run() Address = 0x10aa4f44e (filename not found) [in UE4Editor-Core.dylib]
FRunnableThreadPThread::_ThreadProc(void*) Address = 0x10a9f8887 (filename not found) [in UE4Editor-Core.dylib]
_pthread_body Address = 0x7fff70fd76c1 (filename not found) [in libsystem_pthread.dylib]
_pthread_body Address = 0x7fff70fd756d (filename not found) [in libsystem_pthread.dylib]
thread_start Address = 0x7fff70fd6c5d (filename not found) [in libsystem_pthread.dylib]