I've been running into an issue for the past couple days with a custom Lightning component. I'm trying to create a "Note" component where the user/admin in Lightning App Builder selects an Object and a Record to add the note too. Once I click the lightning button to Save, it throws the following error:

Uncaught AuraClientService.postProcess: error in processing [Maximum call stack size exceeded]
throws at https://jeppesen--anthonydev.lightning.force.com/auraFW/javascript/H9Yiy9uuE9726-4_PM7fkQ/aura_prod.js:34:15.

Here is my component and the controller/helper/Apex methods that are running when the error is thrown.

Markup

<aura:component implements="flexipage:availableForAllPageTypes" access="global" controller="Lightning_Note_Controller"> 
        <aura:attribute name="note" type="Lightning_Note__c"/> 
        <aura:attribute name="recordId" type="String"/> 
        <aura:attribute name="objectType" type="String"/> 
        <aura:attribute name="editNote" type="Boolean" default="false"/> 

        <aura:handler name="init" value="{!this}" action="{!c.doInit}" /> 

        <aura:if isTrue="{!and(v.note.Id == null, !v.editNote)}"> 
                <lightning:button label="Add Note" title="Add Note" onclick="{!c.addNote}"/> 
                <aura:set attribute="else"> 
                        <aura:if isTrue="{!v.editNote}"> 
                                <lightning:button label="Save Note" title="Save Note" onclick="{!c.saveNote}"/> 
                                <lightning:inputRichText value="{!v.note.Note__c}"/> 
                                <aura:set attribute="else"> 
                                        <lightning:button label="Edit Note" title="Edit Note" onclick="{!c.editNote}"/> 
                                        <lightning:formattedRichText value="{!v.note.Note__c}"/> 
                                </aura:set> 
                        </aura:if> 
                </aura:set> 
        </aura:if> 
</aura:component>

Controller

saveNote : function(component, event, helper){
        helper.save(component, event, helper); 
}

Helper

//Saves note record 
save : function(component, event, helper){
        var saveNoteAction = component.get("c.saveNote"); 
        saveNoteAction.setParams({ 
                note : JSON.stringify(component.get("v.note")) 
        }); 
        saveNoteAction.setCallback(this, function(response2) { 
                var responseState2 = response2.getState(); 
                if (responseState2 == "SUCCESS") { 
                        var note = response2.getReturnValue(); 
                        component.set("v.note", note); 
                        component.set("v.editNote", false); 
                } 
        }); 
        $A.enqueueAction(saveNoteAction); 
}

Apex Controller

@AuraEnabled 
public static Lightning_Note__c saveNote(String note){ 
        Lightning_Note__c noteObject = (Lightning_Note__c)JSON.deserialize(note, Lightning_Note__c.class); 
        upsert noteObject; 
        System.debug('Upserted Note: ' + noteObject); 
        return noteObject; 
}

The Apex never shows up in the debug log whenever I check. Also, if I try to insert console log statements in my JS methods, the error is not displayed. Instead, all the console.log() statments repeatedly display in the console and take up all my CPU til I force quit my browser. It's as if the method is running recursively, but I don't see how this could be happening. 

Any help is greatly appreciated.

I created a brand new playground and searched for it in app exchange but no app exists to complete this challenge.

I downloaded the package "OpportunityAlert" to my lightning org and installed it. Unfortunately I cannot find a custom lightning component called "ContactsToday". The only custom component I have is called "OpportunityAlert".

My domain has been registered "https://cunning-goat-246739-dev-ed.lightning.force.com"

What am I doing wrong?