Message Sent To Deallocated Instance When Using Tab Key Only - ios

Question

So I have an view controller with a form like so:
When I use the back and forward buttons on the input accessory view, everything works fine. However, in simulator when I use the tab key on the keyboard to traverse the text fields, and then segue back to the previous view controller, I get the following:
and then this in the console:
I look for zombie objects in Instruments and find this:
but that doesn't provide much help. Any idea why this would ONLY happen when tab is pressed on the keyboard in simulator? It isn't an issue on the device and I can't reproduce it there but I feel like a zombie object needs to be address either way.
and here is my code for that view controller:
in viewDidLoad i'm calling setupInputAccessoryView
func setupInputAccessoryView(){
// Create a button bar for the number pad
let keyboardDoneButtonView = UIToolbar()
keyboardDoneButtonView.sizeToFit()
// Setup the buttons to be put in the toolbar.
let item4 = UIBarButtonItem(title: "Done", style: UIBarButtonItemStyle.Plain, target: self, action: Selector("endEditingNow") )
let item = UIBarButtonItem(title: " < ", style: UIBarButtonItemStyle.Plain, target: self, action: Selector("previousField"))
let item2 = UIBarButtonItem(title: " >", style: UIBarButtonItemStyle.Plain, target: self, action: Selector("nextField"))
let item3 = UIBarButtonItem(barButtonSystemItem: UIBarButtonSystemItem.FlexibleSpace, target: self, action: nil)
if let font = UIFont(name: "Helvetica", size: 17) {
item4.setTitleTextAttributes([NSFontAttributeName: font], forState: UIControlState.Normal)
}
if let font2 = UIFont(name: "Helvetica", size: 26){
item.setTitleTextAttributes([NSFontAttributeName: font2], forState: UIControlState.Normal)
item2.setTitleTextAttributes([NSFontAttributeName: font2], forState: UIControlState.Normal)
}
//Add buttons to toolbar and add as an inputAccessoryView
var toolbarButtons = [item, item2, item3, item4]
keyboardDoneButtonView.setItems(toolbarButtons, animated: false)
keyBoardToolBar = keyboardDoneButtonView
}
and then in textFieldDidBeginEditing I have:
func textFieldDidBeginEditing(textField: UITextField) {
currentTextField = textField
textField.inputAccessoryView = keyBoardToolBar
if (textField == stateField){
statePicker.frame = CGRectZero
statePicker.delegate = self
statePicker.dataSource = self
textField.inputView = statePicker
}else if (textField == countryField){
countryPicker.frame = CGRectZero
countryPicker.delegate = self
countryPicker.dataSource = self
textField.inputView = countryPicker
}
UIView.animateWithDuration(0.5, animations: { () -> Void in
self.scrollView.contentOffset.y = textField.center.y - 30
})
}
and then my selectors for the toolbar buttons
func endEditingNow(){
self.view.endEditing(true)
}
func nextField(){
var nextTag = currentTextField!.tag + 1
self.view.viewWithTag(nextTag)?.becomeFirstResponder()
}
func previousField(){
var nextTag = currentTextField!.tag - 1
self.view.viewWithTag(nextTag)?.becomeFirstResponder()
}