mongoose functions only working on second call

So the weirdest thing is going on. I have a coffeescript class which I use to construct a mongoose schema.

module.exports = class Profit 

    constructor: (Schema, mongoose) ->

        @DailyProfitSchema = new Schema(

            profit:
                type: Number
                default: 0
            percent_profit:
                type: Number
                default: 0   
            day:
                type: Number
                default: 0
        )

        @Day = mongoose.model('Day', @DailyProfitSchema)

        @local_day = null

and here is my update function

update: (funds) ->

    if @local_day?.day is not date.getDate() 
        # new day
        @local_day = new @Day()

        @local_day.save(
            (err, res) ->
                console.log "saving local day"
                if err?
                    console.log err
        )

the weird thing is that when I update

Profit = require '../new_profit'

mongoose = require('mongoose')
mongoose.connect('mongodb://localhost/test')


Schema = mongoose.Schema

profit = new Profit(Schema, mongoose)

funds = 
    amount: 100

profit.update(funds)

nothing is outputted, as opposed to the expected saving local day which should be outputted when @local_day.save() is called.

Okay so this is weird enough, but what's even weirder is that when I change the update function to this

update: (funds) ->

    if @local_day?.day is not date.getDate() 
        # new day
        @local_day = new @Day()

        console.log @local_day.save() # this is the line I added

        @local_day.save(
            (err, res) ->
                console.log "saving local day"
                if err?
                    console.log err
        )

I get the even more unexpected result

undefined
saving local day

What could possibly be causing this?

Also I'm not sure if it's relevant but I'm running mongod as a background process to make the local db work.

Update: Well whatever it was, the problem went away when I stopped using the local db mongodb://localhost/test