diff --git a/Source/Engine/Animations/Graph/AnimGroup.Animation.cpp b/Source/Engine/Animations/Graph/AnimGroup.Animation.cpp
index fd62ec537..a1f2a4565 100644
--- a/Source/Engine/Animations/Graph/AnimGroup.Animation.cpp
+++ b/Source/Engine/Animations/Graph/AnimGroup.Animation.cpp
@@ -2553,9 +2553,15 @@ void AnimGraphExecutor::ProcessGroupFunction(Box* boxBase, Node* node, Value& va
     // Function Input
     case 1:
     {
+        // Skip when graph is too small (eg. preview) and fallback with default value from the function graph
+        if (context.GraphStack.Count() < 2)
+        {
+            value = tryGetValue(node->TryGetBox(1), Value::Zero);
+            break;
+        }
+
         // Find the function call
         AnimGraphNode* functionCallNode = nullptr;
-        ASSERT(context.GraphStack.Count() >= 2);
         Graph* graph;
         for (int32 i = context.CallStack.Count() - 1; i >= 0; i--)
         {
diff --git a/Source/Engine/Particles/Graph/CPU/ParticleEmitterGraph.CPU.Particles.cpp b/Source/Engine/Particles/Graph/CPU/ParticleEmitterGraph.CPU.Particles.cpp
index a47e15275..1a7ba37d1 100644
--- a/Source/Engine/Particles/Graph/CPU/ParticleEmitterGraph.CPU.Particles.cpp
+++ b/Source/Engine/Particles/Graph/CPU/ParticleEmitterGraph.CPU.Particles.cpp
@@ -482,9 +482,15 @@ void ParticleEmitterGraphCPUExecutor::ProcessGroupFunction(Box* box, Node* node,
     // Function Input
     case 1:
     {
+        // Skip when graph is too small (eg. preview) and fallback with default value from the function graph
+        if (context.GraphStack.Count() < 2)
+        {
+            value = tryGetValue(node->TryGetBox(1), Value::Zero);
+            break;
+        }
+
         // Find the function call
         Node* functionCallNode = nullptr;
-        ASSERT(context.GraphStack.Count() >= 2);
         ParticleEmitterGraphCPU* graph;
         for (int32 i = context.CallStackSize - 1; i >= 0; i--)
         {
diff --git a/Source/Engine/Tools/MaterialGenerator/MaterialGenerator.Material.cpp b/Source/Engine/Tools/MaterialGenerator/MaterialGenerator.Material.cpp
index c778c03ee..09ac78e6b 100644
--- a/Source/Engine/Tools/MaterialGenerator/MaterialGenerator.Material.cpp
+++ b/Source/Engine/Tools/MaterialGenerator/MaterialGenerator.Material.cpp
@@ -790,9 +790,18 @@ void MaterialGenerator::ProcessGroupFunction(Box* box, Node* node, Value& value)
     // Function Input
     case 1:
     {
+        // Check the stack count. If only 1 graph is present,
+        // we are processing the graph in isolation (e.g., in the Editor Preview).
+        // In this case, we skip the caller-finding logic and use the node's default value.
+        if (_graphStack.Count() < 2)
+        {
+            // Use the default value from the function input node's box (usually box 1)
+            value = tryGetValue(node->TryGetBox(1), Value::Zero);
+            break;
+        }
+
         // Find the function call
         Node* functionCallNode = nullptr;
-        ASSERT(_graphStack.Count() >= 2);
         Graph* graph;
         for (int32 i = _callStack.Count() - 1; i >= 0; i--)
         {