Second Approach to Fix #5420 & #6988

src/main/java/com/simibubi/create/content/contraptions/Contraption.java

@@ -1150,6 +1150,8 @@ public void addBlocksToWorld(Level world, StructureTransform transform) {
 
 		translateMultiblockControllers(transform);
 
+		GhostPlacementServerLevel ghostLevel = null;
+
 		for (boolean nonBrittles : Iterate.trueAndFalse) {
 			for (StructureBlockInfo block : blocks.values()) {
 				if (nonBrittles == BlockMovementChecks.isBrittle(block.state()))
@@ -1170,12 +1172,25 @@ public void addBlocksToWorld(Level world, StructureTransform transform) {
 				if (blockState.getDestroySpeed(world, targetPos) == -1 || (state.getCollisionShape(world, targetPos)
 					.isEmpty()
 					&& !blockState.getCollisionShape(world, targetPos)
-					.isEmpty())) {
+					.isEmpty()) || world.isOutsideBuildHeight(targetPos) || (state.isAir() && !block.state().isAir())) {
+					state = block.state();
 					if (targetPos.getY() == world.getMinBuildHeight())
 						targetPos = targetPos.above();
 					world.levelEvent(2001, targetPos, Block.getId(state));
-					if (shouldDropBlocks) {
-						Block.dropResources(state, world, targetPos, null);
+					if (!shouldDropBlocks)
+						continue;
+					if (ghostLevel == null && world instanceof ServerLevel serverWorld)
+						ghostLevel = new GhostPlacementServerLevel(serverWorld);
+					if (ghostLevel != null) {
+						ghostLevel.setBlock(targetPos, state, Block.UPDATE_NONE);
+						BlockEntity be = ghostLevel.getBlockEntity(targetPos);
+						if (be != null) {
+							CompoundTag tag = block.nbt();
+							tag = NBTProcessors.process(state, be, tag, false);
+							if (tag != null)
+								be.load(tag);
+						}
+						ghostLevel.destroyBlock(targetPos, true);
 					}
 					continue;
 				}

src/main/java/com/simibubi/create/content/contraptions/GhostPlacementServerLevel.java

@@ -0,0 +1,70 @@
+package com.simibubi.create.content.contraptions;
+
+import javax.annotation.Nullable;
+
+import net.createmod.catnip.levelWrappers.WrappedServerLevel;
+import net.minecraft.core.BlockPos;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.entity.Entity;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.level.block.Block;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.EntityBlock;
+import net.minecraft.world.level.block.entity.BlockEntity;
+import net.minecraft.world.level.block.state.BlockState;
+
+import java.util.HashMap;
+import java.util.Map;
+
+public class GhostPlacementServerLevel extends WrappedServerLevel {
+
+	protected final Map<BlockPos, BlockState> blockStates = new HashMap<>();
+	protected final Map<BlockPos, BlockEntity> blockEntities = new HashMap<>();
+
+	public GhostPlacementServerLevel(ServerLevel level) {
+		super(level);
+	}
+
+	@Override
+	public boolean setBlock(BlockPos pos, BlockState newState, int flags) {
+		pos = pos.immutable();
+		getBlockState(pos).onRemove(this, pos, newState,false);
+		blockStates.put(pos, newState);
+		return true;
+	}
+
+	@Override
+	public BlockState getBlockState(BlockPos pos) {
+		return blockStates.getOrDefault(pos, Blocks.AIR.defaultBlockState());
+	}
+
+	@Nullable
+	public BlockEntity getBlockEntity(BlockPos pos) {
+		BlockState blockState = getBlockState(pos);
+		BlockEntity blockEntity = blockEntities.getOrDefault(pos, null);
+		if (blockState.hasBlockEntity() && blockEntity == null) {
+			blockEntity = ((EntityBlock) blockState.getBlock()).newBlockEntity(pos, blockState);
+			if (blockEntity != null)
+				blockEntity.setLevel(this);
+			pos = pos.immutable();
+			blockEntities.put(pos, blockEntity);
+		}
+		return blockEntity;
+	}
+
+	@Override
+	public void removeBlockEntity(BlockPos pos) {
+		blockEntities.remove(pos);
+	}
+
+	@Override
+	public boolean destroyBlock(BlockPos pos, boolean dropBlock, @Nullable Entity entity, int recursionLeft) {
+		BlockState blockState = getBlockState(pos);
+		if (blockState.isAir())
+			return false;
+		if (dropBlock)
+			Block.dropResources(blockState, this, pos, getBlockEntity(pos), entity, ItemStack.EMPTY);
+		setBlock(pos, Blocks.AIR.defaultBlockState(), Block.UPDATE_NONE);
+		return true;
+	}
+}