I made a lasso item in forge 1.20.1 that can be used as grappling hook and to move entities towards it. When I test it on singleplayer it works flawlessly, but if I use it on servers it has a deflection. Also if I have used it once, all projectiles receive a deflection until I leave.

My Item class:

 

package com.kuikenpower.falidsmp.init.item;

import java.util.List;

import com.kuikenpower.falidsmp.entities.HookEntity;
import net.minecraft.core.BlockPos;
import net.minecraft.network.protocol.game.ClientboundLevelParticlesPacket;
import net.minecraft.server.level.ServerPlayer;
import net.minecraft.world.InteractionHand;
import net.minecraft.world.InteractionResultHolder;
import net.minecraft.world.effect.MobEffectInstance;
import net.minecraft.world.effect.MobEffects;
import net.minecraft.world.entity.Entity;
import net.minecraft.world.entity.Entity.RemovalReason;
import net.minecraft.world.entity.EntityType;
import net.minecraft.world.entity.ambient.Bat;
import net.minecraft.world.entity.item.ItemEntity;
import net.minecraft.world.entity.player.Player;
import net.minecraft.world.item.Item;
import net.minecraft.world.item.ItemStack;
import net.minecraft.world.item.Items;
import net.minecraft.world.level.Level;
import net.minecraft.world.phys.AABB;
import net.minecraft.world.phys.Vec3;

public class MesaLasso extends Item  {
	public HookEntity entity;
	
	public Vec3 startPoint;
	public Vec3 controlPoint;
	public Vec3 endPoint;
	public double lastDistance;
	public long startTime;
	public Bat leashHolder;
	private static final long MOVEMENT_DURATION = 1000;
	public AABB leashArea;
	
	public MesaLasso(Properties p_41383_) {
		super(p_41383_);
		// TODO Auto-generated constructor stub
	}
	
	public static Vec3 lerpBetweenPoints(Vec3 start, Vec3 end, float percentage) {
	    double x = start.x + (end.x - start.x) * percentage;
	    double y = start.y + (end.y - start.y) * percentage;
	    double z = start.z + (end.z - start.z) * percentage;
	    return new Vec3(x, y, z);
	}

	public Vec3 getCurvePosition(float percentage) {
	    // Calculate the position between the start and end points along the y-axis
	    double y = startPoint.y + (endPoint.y - startPoint.y) * percentage;
	    
	    double curveFactor = 2.0;
	    y += curveFactor * Math.sin(percentage * Math.PI * ((2 * Math.PI) / 8));

	    // Use the original x and z coordinates from the start point
	    double x = startPoint.x + (endPoint.x - startPoint.x) * percentage;
	    double z = startPoint.z + (endPoint.z - startPoint.z) * percentage;

	    return new Vec3(x, y, z);
	}
	
	@Override
	public InteractionResultHolder<ItemStack> use(Level level, Player player, InteractionHand p_41434_) {
		if(entity != null) {
			if(leashHolder != null) {
				entity.blockColliding = false;
            	entity.kill();
            	leashArea = new AABB(leashHolder.position().x + 2, leashHolder.position().y + 2, leashHolder.position().z + 2, leashHolder.position().x - 2, leashHolder.position().y - 2, leashHolder.position().z - 2);
            	leashHolder.remove(RemovalReason.DISCARDED);
            	killLead(level);
			}
		}
		entity = new HookEntity(level, player);
        level.addFreshEntity(entity);
        if(entity != null) {
        	leashHolder = new Bat(EntityType.BAT, level);
			leashHolder.setPos(entity.position());
			leashHolder.addTag("leashHolder");
			leashHolder.setInvulnerable(true);
        	leashHolder.addEffect(new MobEffectInstance(MobEffects.INVISIBILITY, 10, 10, false, false));
			level.addFreshEntity(leashHolder);
        }
		return super.use(level, player, p_41434_);
	}
	
	@Override
	public void inventoryTick(ItemStack p_41404_, Level p_41405_, Entity player, int p_41407_, boolean p_41408_) {
		if(entity != null) {
			if(leashHolder != null) {
				if(entity.entityColliding == false) {
					leashHolder.setPos(entity.position());
					leashHolder.addEffect(new MobEffectInstance(MobEffects.INVISIBILITY, 10, 10, false, false));
				}
			}
			double deltaX = entity.position().x - player.position().x;
	        double deltaY = entity.position().y - player.position().y;
	        double deltaZ = entity.position().z - player.position().z;
	        Vec3 midPoint = new Vec3((entity.position().x + player.position().x) * 0.5f, (entity.position().y + player.position().y) * 0.5f, (entity.position().z + player.position().z) * 0.5f);
	        double Yangle = Math.atan2(deltaZ, deltaX) * (180 / Math.PI) + 90f;
			double dX = (Math.sin(Yangle)) * 0.25;
	    	double dZ = (Math.cos(Yangle)) * 0.25;
	        if(deltaZ < 0)
	        {
	        	deltaZ *= -1;
	        }
	        double Xangle = Math.atan(deltaY / deltaZ) * (180 / Math.PI);
	    	double dY = (Math.sin(Xangle)) * 0.25;
	    	float hLength = (float)Math.sqrt((deltaX * deltaX) + (deltaZ * deltaZ));
	    	float length = (float)Math.sqrt((hLength * hLength) + (deltaY * deltaY));
	    	float tCrease = 0.25f / length;
	    	for (float t = 0; t <= 1; t += tCrease) {
	    	    double x = player.position().x + (entity.position().x - player.position().x) * t;
	    	    double y = (player.position().y + 1f) + (entity.position().y - (player.position().y + 1)) * t;
	    	    double z = player.position().z + (entity.position().z - player.position().z) * t;
			}
			if(entity.blockCollidingOnce)
			{
				startPoint = player.position();
				endPoint = new Vec3(entity.position().x, entity.position().y + 2.5, entity.position().z);
				startTime = System.currentTimeMillis(); 
				entity.blockCollidingOnce = false;
				
			}
			if(entity.blockColliding) 
			{
		        double dx = endPoint.x - player.position().x;
	            double dy = endPoint.y - player.position().y;
	            double dz = endPoint.z - player.position().z;

	            double distanceToTarget = Math.sqrt(dx * dx + dy * dy + dz * dz);

	            if (distanceToTarget > 0.5) {
	                dx /= distanceToTarget;
	                dy /= distanceToTarget;
	                dz /= distanceToTarget;
	                player.setDeltaMovement(dx * 1, dy * 1 , dz * 1);
	            } else {
	            	entity.blockColliding = false;
	            	entity.kill();
	            	leashArea = new AABB(leashHolder.position().x + 2, leashHolder.position().y + 2, leashHolder.position().z + 2, leashHolder.position().x - 2, leashHolder.position().y - 2, leashHolder.position().z - 2);
	            	leashHolder.remove(RemovalReason.DISCARDED);
	            	killLead(p_41405_);
	            }
			}
			if(entity.entityCollidingOnce)
			{
				startPoint = player.position();
				endPoint = new Vec3(entity.position().x, entity.position().y + 2.5, entity.position().z);
				startTime = System.currentTimeMillis(); 
				entity.entityCollidingOnce = false;
				
			}
			if(entity.entityColliding) 
			{
				leashHolder.setPos(entity.hitEntity.position());
				leashHolder.addEffect(new MobEffectInstance(MobEffects.INVISIBILITY, 10, 10, false, false));
		        double dx = player.position().x - entity.hitEntity.position().x;
	            double dy = player.position().y - entity.hitEntity.position().y;
	            double dz = player.position().z - entity.hitEntity.position().z;

	            double distanceToTarget = Math.sqrt(dx * dx + dy * dy + dz * dz);

	            if (distanceToTarget > 0.5) {
	                dx /= distanceToTarget;
	                dy /= distanceToTarget;
	                dz /= distanceToTarget;
	                entity.hitEntity.setDeltaMovement(dx * 1, dy * 1 , dz * 1);
	            } else {
	            	entity.entityColliding = false;
	            	entity.kill();
	            	leashArea = new AABB(leashHolder.position().x + 2, leashHolder.position().y + 2, leashHolder.position().z + 2, leashHolder.position().x - 2, leashHolder.position().y - 2, leashHolder.position().z - 2);
	            	leashHolder.remove(RemovalReason.DISCARDED);
	            	killLead(p_41405_);
	            }
			}
		}
		super.inventoryTick(p_41404_, p_41405_, player, p_41407_, p_41408_);
	}
	
	private boolean isPlayerCollidingWithBlock(Entity player) {
	    AABB playerBoundingBox = player.getBoundingBox();

	    int playerX = (int) player.getX();
	    int playerY = (int) player.getX();
	    int playerZ = (int) player.getZ();

	    for (int x = playerX - 1; x <= playerX + 1; x++) {
	        for (int y = playerY - 1; y <= playerY + 1; y++) {
	            for (int z = playerZ - 1; z <= playerZ + 1; z++) {
	                if (player.level().getBlockState(new BlockPos(x, y, z)).getCollisionShape(player.level(), new BlockPos(x, y, z)).isEmpty()) {
	                    continue;
	                }
	                if (playerBoundingBox.intersects(new AABB(x, y, z, x + 1, y + 1, z + 1))) {
	                    return true;
	                }
	            }
	        }
	    }

	    return false; // Player is not colliding with any block.
	}
	
	private void sendPacketToAllPlayers(ClientboundLevelParticlesPacket packet, Player sourcePlayer) {
		if(sourcePlayer.getServer() != null) {
			for (ServerPlayer player : sourcePlayer.getServer().getPlayerList().getPlayers()) {
				player.connection.send(packet);
			}
		}
	}
	
	public void killLead(Level level) 
	{
		if(leashArea != null) {
			List<ItemEntity> list = level.getEntitiesOfClass(ItemEntity.class, leashArea);
			for(ItemEntity item : list) {
				if(item.getItem().getItem() == Items.SHIELD);
				{
					item.kill();
				}
			}
		}
	}
}

 

When I try to add my HookEntity class it says I am spamming.