diff --git a/src/main/java/gregtech/api/recipes/RecipeBuilder.java b/src/main/java/gregtech/api/recipes/RecipeBuilder.java
index d12ec1afb90..d7d8884daa7 100644
--- a/src/main/java/gregtech/api/recipes/RecipeBuilder.java
+++ b/src/main/java/gregtech/api/recipes/RecipeBuilder.java
@@ -828,7 +828,7 @@ protected static void multiplyInputsAndOutputs(List<GTRecipeInput> newRecipeInpu
             if (ri.isNonConsumable()) {
                 newRecipeInputs.add(ri);
             } else {
-                newRecipeInputs.add(ri.withAmount(ri.getAmount() * numberOfOperations));
+                newRecipeInputs.add(ri.copyWithAmount(ri.getAmount() * numberOfOperations));
             }
         });
 
@@ -836,7 +836,7 @@ protected static void multiplyInputsAndOutputs(List<GTRecipeInput> newRecipeInpu
             if (fi.isNonConsumable()) {
                 newFluidInputs.add(fi);
             } else {
-                newFluidInputs.add(fi.withAmount(fi.getAmount() * numberOfOperations));
+                newFluidInputs.add(fi.copyWithAmount(fi.getAmount() * numberOfOperations));
             }
         });
 
diff --git a/src/main/java/gregtech/api/util/OverlayedItemHandler.java b/src/main/java/gregtech/api/util/OverlayedItemHandler.java
index 83c63422930..dcd73ddb281 100644
--- a/src/main/java/gregtech/api/util/OverlayedItemHandler.java
+++ b/src/main/java/gregtech/api/util/OverlayedItemHandler.java
@@ -58,7 +58,8 @@ public int insertStackedItemStack(@NotNull ItemStack stack, int amountToInsert)
             ItemStack slotKey = this.slots[i].getItemStack();
             if (slotKey.isEmpty() || ItemStackHashStrategy.comparingAllButCount().equals(slotKey, stack)) {
                 // if the slot is not full
-                int canInsertUpTo = this.slots[i].getSlotLimit() - this.slots[i].getCount();
+                int canInsertUpTo = Math.min(this.slots[i].getSlotLimit() - this.slots[i].getCount(),
+                        stack.getMaxStackSize());
                 if (canInsertUpTo > 0) {
                     int insertedAmount = Math.min(canInsertUpTo, amountToInsert);
                     this.slots[i].setItemStack(stack.copy()); // this copy may not be need, needs further tests
diff --git a/src/test/java/gregtech/api/recipes/logic/IParallelableRecipeLogicTest.java b/src/test/java/gregtech/api/recipes/logic/IParallelableRecipeLogicTest.java
index 8ab302939fa..882d9287e6a 100644
--- a/src/test/java/gregtech/api/recipes/logic/IParallelableRecipeLogicTest.java
+++ b/src/test/java/gregtech/api/recipes/logic/IParallelableRecipeLogicTest.java
@@ -12,6 +12,7 @@
 import gregtech.api.recipes.Recipe;
 import gregtech.api.recipes.RecipeBuilder;
 import gregtech.api.recipes.RecipeMap;
+import gregtech.api.recipes.RecipeMapBuilder;
 import gregtech.api.recipes.builders.BlastRecipeBuilder;
 import gregtech.api.unification.material.Materials;
 import gregtech.api.util.GTUtility;
@@ -24,6 +25,7 @@
 import gregtech.common.metatileentities.multi.multiblockpart.MetaTileEntityMultiblockPart;
 
 import net.minecraft.init.Blocks;
+import net.minecraft.init.Items;
 import net.minecraft.item.ItemStack;
 import net.minecraft.util.ResourceLocation;
 import net.minecraft.world.World;
@@ -38,8 +40,7 @@
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
 
-import static org.hamcrest.CoreMatchers.is;
-import static org.hamcrest.CoreMatchers.nullValue;
+import static org.hamcrest.CoreMatchers.*;
 
 public class IParallelableRecipeLogicTest {
 
@@ -713,6 +714,44 @@ public MetaTileEntity getMetaTileEntity() {
         MatcherAssert.assertThat(outputRecipe, nullValue());
     }
 
+    @Test
+    public void findParallelRecipe_SmallMaxStackSize() {
+        MetaTileEntityElectricBlastFurnace EBF = initEBF(521);
+
+        int parallelLimit = 4;
+
+        // Create a recipe Map to be used for testing
+        RecipeMap<BlastRecipeBuilder> map = new RecipeMapBuilder<>("electric_blast_furnace", new BlastRecipeBuilder())
+                .itemInputs(3).itemOutputs(2).fluidInputs(1).fluidOutputs(1).build();
+
+        // Create a simple recipe to be used for testing
+        // Use an output item with small max stack size
+        Recipe recipe = map.recipeBuilder()
+                .inputs(new ItemStack(Blocks.COBBLESTONE))
+                .outputs(new ItemStack(Items.ELYTRA))
+                .blastFurnaceTemp(1000)
+                .EUt(30).duration(100)
+                .build().getResult();
+
+        IParallelableRecipeLogic logic = new ParallelableTestLogic(EBF, map, ParallelLogicType.MULTIPLY);
+
+        // Populate the Input Bus
+        importItemBus.getImportItems().insertItem(0, new ItemStack(Blocks.COBBLESTONE, 16), false);
+
+        // Saturate the export bus, except for one slot
+        exportItemBus.getExportItems().insertItem(0, new ItemStack(Blocks.BONE_BLOCK, 16), false);
+        exportItemBus.getExportItems().insertItem(1, new ItemStack(Blocks.BONE_BLOCK, 16), false);
+        exportItemBus.getExportItems().insertItem(2, new ItemStack(Blocks.BONE_BLOCK, 16), false);
+
+        RecipeBuilder<?> parallelRecipe = logic.findMultipliedParallelRecipe(map, recipe,
+                importItemBus.getImportItems(), importFluidBus.getImportFluids(),
+                exportItemBus.getExportItems(), exportFluidBus.getExportFluids(), parallelLimit, Integer.MAX_VALUE,
+                EBF);
+
+        MatcherAssert.assertThat(parallelRecipe, notNullValue());
+        MatcherAssert.assertThat(parallelRecipe.getParallel(), is(1));
+    }
+
     @Test
     public void applyParallelBonus_Test() {
         MetaTileEntityElectricBlastFurnace EBF = initEBF(518);