Mixin does nothing

I’m using mixin to improve Sponge mod but unfortunately its not properly applied as nothing is printed but the regular message. ids.length != 2 is given.

how can I improve this? I want to replace a Sponge method.

package cabbage

import net.minecraft.world.World;
import org.apache.logging.log4j.Level;
import org.spongepowered.api.block.BlockType;
import org.spongepowered.asm.mixin.Mixin;
import org.spongepowered.asm.mixin.Shadow;
import org.spongepowered.asm.util.PrettyPrinter;
import org.spongepowered.common.SpongeImpl;
import org.spongepowered.common.config.SpongeConfig;
import org.spongepowered.common.config.category.BlockCapturingCategory;
import org.spongepowered.common.config.category.BlockCapturingModCategory;
import org.spongepowered.common.interfaces.world.IMixinWorldServer;
import org.spongepowered.common.mixin.blockcapturing.MixinBlock_BlockCapturing;
import org.spongepowered.common.config.type.GeneralConfigBase;

@Mixin(value = MixinBlock_BlockCapturing.class, priority = 9999)
public abstract class MixinBlockCapturing implements BlockType {
    @Shadow
    private boolean processTickChangesImmediately;

    public void initializeBlockCapturingState(World worldIn) {
        SpongeConfig<? extends GeneralConfigBase> activeConfig = ((IMixinWorldServer) worldIn).getActiveConfig();
        BlockCapturingCategory blockCapturing = activeConfig.getConfig().getBlockCapturing();
        String[] ids = this.getId().split(":");

        if (ids.length != 2) {
            System.out.println("Try get bong");
            if (true) {
            } else {
                final PrettyPrinter printer = new PrettyPrinter(60).add("Malformatted Block ID discovered!").centre().hr()
                        .addWrapped(60, "Sponge has found a malformatted block id when trying to"
                                + " load configurations for the block id. The printed out block id"
                                + "is not originally from sponge, and should be brought up with the"
                                + "mod developer as the registration for this block is not likely"
                                + "to work with other systems and assumptions of having a properly"
                                + "formatted block id.")
                        .add("%s : %s", "Malformed ID", this.getId())
                        .add("%s : %s", "Discovered id array", ids)
                        .add();
                final String id = ids[0];
                ids = new String[]{"unknown", id};
                printer
                        .add("Sponge will attempt to work around this by using the provided generated id:")
                        .add("%s : %s", "Generated ID", ids)
                        .log(SpongeImpl.getLogger(), Level.WARN);
            }
        }
        String modId = ids[0];
        String name = ids[1];

        BlockCapturingModCategory modCapturing = blockCapturing.getModMappings().get(modId);
        if (modCapturing == null && blockCapturing.autoPopulateData()) {
            modCapturing = new BlockCapturingModCategory();
            blockCapturing.getModMappings().put(modId.toLowerCase(), modCapturing);
            modCapturing.getBlockMap().put(name.toLowerCase(), false);
            if (blockCapturing.autoPopulateData()) {
                activeConfig.save();
            }
            return;
        } else if (modCapturing != null) {
            if (!modCapturing.isEnabled()) {
                this.processTickChangesImmediately = false;
                return;
            }

            Boolean processImmediately = modCapturing.getBlockMap().get(name.toLowerCase());
            if (processImmediately != null) {
                this.processTickChangesImmediately = processImmediately;
            }
        }

        if (blockCapturing.autoPopulateData()) {
            activeConfig.save();
        }
    }
}

this is my build.gradle

buildscript {
    repositories {
        maven {
            name = 'forge'
            url = 'http://files.minecraftforge.net/maven'
        }
        flatDir {
            dirs "lib"
        }
        maven {
            name = 'sponge'
            url = 'https://repo.spongepowered.org/maven'
        }
    }

    dependencies {
        classpath 'net.minecraftforge.gradle:ForgeGradle:2.3-SNAPSHOT'
        classpath 'org.spongepowered:mixingradle:0.5-SNAPSHOT'
    }
}

plugins {
    id 'java'
    id 'org.spongepowered.plugin' version '0.8.1'
    id 'net.minecrell.vanillagradle.server' version '2.2-6'
}

apply plugin: 'org.spongepowered.mixin'

sourceCompatibility = '1.8'
targetCompatibility = '1.8'

version = '0.3'

repositories {
    flatDir {
        dirs "lib"
    }
}

dependencies {
    compile 'org.spongepowered:spongeapi:7.0.0'
    compile 'org.spongepowered:spongecommon:7.1.0-SNAPSHOT:dev'
    compile 'org.spongepowered:mixin:0.7.5-SNAPSHOT'
    compileOnly name: "mod-decor"
}

minecraft {
    version = '1.12.2'
    mappings = "snapshot_20180104"
    makeObfSourceJar = false
}

mixin {
    add sourceSets.main, "mixins.refmap.json"
}

jar {
    manifest.attributes(
            'TweakClass': 'org.spongepowered.asm.launch.MixinTweaker',
            'MixinConfigs': 'mixins.gss.json',
            'FMLCorePluginContainsFMLMod': 'true',
    )
}

and this my mixinconfig in resources folder

{
  "required": true,
  "minVersion": "0.5.7",
  "package": "cabbage",
  "refmap": "mixins.refmap.json",
  "target": "@env(DEFAULT)",
  "compatibilityLevel": "JAVA_8",
  "server": [
    "MixinMinecraftServer"
  ],
  "injectors": {
    "defaultRequire": 1
  }
}

You can’t mixin a mixin… What are you actually trying to change? compared to the existing code?

Likewise, the method can’t be overwritten, but the injection can be rewritten by substituting the mixin for another one.

I want to make a workaround for this bug with a fallback block registry.

is there any info about substituting a mixin available? I didnt find anything and just renaming the class to MixinBlock_BlockCapturing was unsucessful