diff --git a/src/main/java/com/simibubi/create/content/contraptions/components/structureMovement/Contraption.java b/src/main/java/com/simibubi/create/content/contraptions/components/structureMovement/Contraption.java
index 32f9a2a34..9480d7e04 100644
--- a/src/main/java/com/simibubi/create/content/contraptions/components/structureMovement/Contraption.java
+++ b/src/main/java/com/simibubi/create/content/contraptions/components/structureMovement/Contraption.java
@@ -119,7 +119,7 @@ public abstract class Contraption {
 
 	public Optional<List<AxisAlignedBB>> simplifiedEntityColliders;
 	public AbstractContraptionEntity entity;
-	public CombinedInvWrapper inventory;
+	public ContraptionInvWrapper inventory;
 	public CombinedTankWrapper fluidInventory;
 	public AxisAlignedBB bounds;
 	public BlockPos anchor;
@@ -252,7 +252,7 @@ public abstract class Contraption {
 			.stream()
 			.map(MountedStorage::getItemHandler)
 			.collect(Collectors.toList());
-		inventory = new CombinedInvWrapper(Arrays.copyOf(list.toArray(), list.size(), IItemHandlerModifiable[].class));
+		inventory = new ContraptionInvWrapper(Arrays.copyOf(list.toArray(), list.size(), IItemHandlerModifiable[].class));
 
 		List<IFluidHandler> fluidHandlers = fluidStorage.values()
 			.stream()
@@ -341,7 +341,7 @@ public abstract class Contraption {
 		// Bearings potentially create stabilized sub-contraptions
 		if (AllBlocks.MECHANICAL_BEARING.has(state))
 			moveBearing(pos, frontier, visited, state);
-		
+
 		// WM Bearings attach their structure when moved
 		if (AllBlocks.WINDMILL_BEARING.has(state))
 			moveWindmillBearing(pos, frontier, visited, state);
@@ -739,7 +739,7 @@ public abstract class Contraption {
 		for (MountedFluidStorage mountedStorage : fluidStorage.values())
 			fluidHandlers[index++] = mountedStorage.getFluidHandler();
 
-		inventory = new CombinedInvWrapper(handlers);
+		inventory = new ContraptionInvWrapper(handlers);
 		fluidInventory = new CombinedTankWrapper(fluidHandlers);
 
 		if (nbt.contains("BoundsFront"))
@@ -1053,8 +1053,10 @@ public abstract class Contraption {
 				BlockFlags.IS_MOVING | BlockFlags.DEFAULT, 512);
 		}
 
-		for (int i = 0; i < inventory.getSlots(); i++)
-			inventory.setStackInSlot(i, ItemStack.EMPTY);
+		for (int i = 0; i < inventory.getSlots(); i++) {
+			if (!inventory.isSlotExternal(i))
+				inventory.setStackInSlot(i, ItemStack.EMPTY);
+		}
 		for (int i = 0; i < fluidInventory.getTanks(); i++)
 			fluidInventory.drain(fluidInventory.getFluidInTank(i), FluidAction.EXECUTE);
 
@@ -1261,4 +1263,24 @@ public abstract class Contraption {
 			return pos.equals(te.getPos());
 		}
 	}
+
+	public static class ContraptionInvWrapper extends CombinedInvWrapper {
+		protected final boolean isExternal;
+
+		public ContraptionInvWrapper(boolean isExternal, IItemHandlerModifiable... itemHandler) {
+			super(itemHandler);
+			this.isExternal = isExternal;
+		}
+
+		public ContraptionInvWrapper(IItemHandlerModifiable... itemHandler) {
+			this(false, itemHandler);
+		}
+
+		public boolean isSlotExternal(int slot) {
+			if (isExternal)
+				return true;
+			IItemHandlerModifiable handler = getHandlerFromIndex(getIndexForSlot(slot));
+			return handler instanceof ContraptionInvWrapper && ((ContraptionInvWrapper) handler).isSlotExternal(slot);
+		}
+	}
 }
diff --git a/src/main/java/com/simibubi/create/content/contraptions/components/structureMovement/mounted/MountedContraption.java b/src/main/java/com/simibubi/create/content/contraptions/components/structureMovement/mounted/MountedContraption.java
index 97b75e778..fae052d36 100644
--- a/src/main/java/com/simibubi/create/content/contraptions/components/structureMovement/mounted/MountedContraption.java
+++ b/src/main/java/com/simibubi/create/content/contraptions/components/structureMovement/mounted/MountedContraption.java
@@ -53,7 +53,7 @@ public class MountedContraption extends Contraption {
 	protected ContraptionType getType() {
 		return ContraptionType.MOUNTED;
 	}
-	
+
 	@Override
 	public boolean assemble(World world, BlockPos pos) throws AssemblyException {
 		BlockState state = world.getBlockState(pos);
@@ -61,17 +61,17 @@ public class MountedContraption extends Contraption {
 			return false;
 		if (!searchMovedStructure(world, pos, null))
 			return false;
-		
+
 		Axis axis = state.get(RAIL_SHAPE) == RailShape.EAST_WEST ? Axis.X : Axis.Z;
 		addBlock(pos, Pair.of(new BlockInfo(pos, AllBlocks.MINECART_ANCHOR.getDefaultState()
 			.with(BlockStateProperties.HORIZONTAL_AXIS, axis), null), null));
-		
+
 		if (blocks.size() == 1)
 			return false;
-		
+
 		return true;
 	}
-	
+
 	@Override
 	protected boolean addToInitialFrontier(World world, BlockPos pos, Direction direction, Queue<BlockPos> frontier) {
 		frontier.clear();
@@ -149,18 +149,18 @@ public class MountedContraption extends Contraption {
 	protected boolean customBlockRemoval(IWorld world, BlockPos pos, BlockState state) {
 		return AllBlocks.MINECART_ANCHOR.has(state);
 	}
-	
+
 	@Override
 	public boolean canBeStabilized(Direction facing, BlockPos localPos) {
 		return true;
 	}
-	
+
 	@Override
 	public void addExtraInventories(Entity cart) {
 		if (!(cart instanceof IInventory))
 			return;
-		IItemHandlerModifiable handlerFromInv = new InvWrapper((IInventory) cart);
-		inventory = new CombinedInvWrapper(handlerFromInv, inventory);
+		IItemHandlerModifiable handlerFromInv = new ContraptionInvWrapper(true, new InvWrapper((IInventory) cart));
+		inventory = new ContraptionInvWrapper(handlerFromInv, inventory);
 	}
 
 	@Override