Strange Error

//variables
args = "$$echo"

//affected code
response = response.replaceAll(Pattern.quote("#args#"),args);

//Error
20:40:31.379 [Event Dispatch Thread] ERROR sx.blah.discord.Discord4J - Unhandled exception caught dispatching event MessageReceivedEvent
java.lang.IllegalArgumentException: Illegal group reference
    at java.util.regex.Matcher.appendReplacement(Matcher.java:857)
    at java.util.regex.Matcher.replaceAll(Matcher.java:955)
    at java.lang.String.replaceAll(String.java:2223)
    at Handlers.CCHandler.tagSystem(CCHandler.java:73)
    at Handlers.CCHandler.handleCommand(CCHandler.java:60)
    at Handlers.CCHandler.<init>(CCHandler.java:44)
    at Handlers.MessageHandler.<init>(MessageHandler.java:95)
    at Listeners.AnnotationListener.onMessageRecivedEvent(AnnotationListener.java:160)
    at sun.reflect.GeneratedMethodAccessor8.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at sx.blah.discord.api.events.EventDispatcher.lambda$null$8(EventDispatcher.java:282)
    at java.util.concurrent.CopyOnWriteArrayList.forEach(CopyOnWriteArrayList.java:890)
    at sx.blah.discord.api.events.EventDispatcher.lambda$null$9(EventDispatcher.java:280)
    at java.util.concurrent.ConcurrentHashMap.forEach(ConcurrentHashMap.java:1597)
    at sx.blah.discord.api.events.EventDispatcher.lambda$null$10(EventDispatcher.java:279)
    at java.util.stream.ForEachOps$ForEachOp$OfRef.accept(ForEachOps.java:184)
    at java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:193)
    at java.util.stream.ReferencePipeline$2$1.accept(ReferencePipeline.java:175)
    at java.util.concurrent.ConcurrentHashMap$EntrySpliterator.forEachRemaining(ConcurrentHashMap.java:3606)
    at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:481)
    at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:471)
    at java.util.stream.ForEachOps$ForEachOp.evaluateSequential(ForEachOps.java:151)
    at java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(ForEachOps.java:174)
    at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
    at java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:418)
    at sx.blah.discord.api.events.EventDispatcher.lambda$dispatch$15(EventDispatcher.java:278)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)