I get such an error in the console and am using this code.

@SubscribeEvent
    public static void onMineBlock(PlayerEvent.BreakSpeed event){
        event.getPlayer().getCapability(Capabilities.PLAYER_SKILLS).ifPresent(skills -> {
            for(AbstractSkill skill : skills.getSkills()){
                if(skill instanceof MineSkill){
                    event.setNewSpeed(event.getOriginalSpeed() * skill.getLevel() + 0.5f);
                    System.out.println("ORIGINAL: " + event.getOriginalSpeed());
                    System.out.println("NEW: " + event.getNewSpeed());
                }
            }
        });
    }

[Server thread/WARN] [net.minecraft.server.level.ServerPlayerGameMode/]: Mismatch in destroy block pos: BlockPos{x=0, y=0, z=0} BlockPos{x=16, y=94, z=13}

Did you send your capabilities to the client? 

i.e. do both the client and server agree on the break speed.

19 minutes ago, warjort said:

Did you send your capabilities to the client? 

i.e. do both the client and server agree on the break speed.

I do not send any packets, what, where and what should be included if should.

1 hour ago, Squander said:

I get such an error in the console and am using this code.

Are you sure PlayerEvent.BreakSpeed cause the error?

Haven't we already been through this discussion? https://forums.minecraftforge.net/topic/115010-1182-capability/

It doesn't look like you followed my advice there.

Quote

Are you sure PlayerEvent.BreakSpeed cause the error?

If you look at what could cause this problem, it would be because the server thinks the block is "instamine", but the client does not.

So the client is sending block break progress events to the server. But the server thinks the block is already broken.

18 minutes ago, warjort said:

If you look at what could cause this problem, it would be because the server thinks the block is "instamine", but the client does not.

So the client is sending block break progress events to the server. But the server thinks the block is already broken.

I should send the packet from server to client or client to server and what it should contain?

Quote

I should send the packet from server to client or client to server

Which side already has the data and where is it missing?

Quote

what it should contain? 

Your capability data.

 

You need to spend time thinking about this, you don't seem to have a clear understanding of what the problem is or what you need to do solve it.

public class MineSkillSyncPacket {
    private int level;

    public MineSkillSyncPacket(int level){
        this.level = level;
    }

    public MineSkillSyncPacket(FriendlyByteBuf buf){
        new MineSkillSyncPacket(buf.readVarInt());
    }

    public void encode(FriendlyByteBuf buf){
        buf.writeVarInt(this.level);
    }

    public boolean handler(Supplier<NetworkEvent.Context> supplier){
        NetworkEvent.Context ctx = supplier.get();
        ctx.enqueueWork(() -> {
            MineSkillData.setLevel(this.level);
        });
        return true;
    }

    public static void register(int id){
        PacketHandler.INSTANCE.messageBuilder(MineSkillSyncPacket.class, id, NetworkDirection.PLAY_TO_CLIENT)
                .decoder(MineSkillSyncPacket::new)
                .encoder(MineSkillSyncPacket::encode)
                .consumer(MineSkillSyncPacket::handler).add();
    }
}

This is my packet, I have to send it from the server to the client, but I don't know where to call the sending methods.