It crashes in FAssetThumbnailPool::Tick( float DeltaTime ) RenderThumbnail as far as I can remember. My temporary fix was to add a && !Asset->IsPendingKill() to if ( RenderInfo != NULL && RenderInfo->Renderer != NULL && !Asset->IsPendingKill() ) in the Tick function, but that’s not right, as I end-up with an empty thumbnail for the asset that failed to import :). I can live with that for the moment but thought you might have a better fix.