Keyboard will not stay in numeric/symbol layout

I've been maintaining an app that uses a TableView for a input form, with textFields on each row to take input. But recently a behaviour has cropped up for iPhone that is annoying our users. When they are inputting into a textfield, and they swap to the numeric/symbol layout then type a single character, it automatically toggles back to alphabet straight away. This is annoying when they have to type a long number/etc. where they have to toggle to the other layout for every single character.

I've stripped it back to a barebones snippet that still has the issue, could someone please tell me how to correct this, or what I'm doing wrong? Or is this something that needs to be logged as an issue?

createform = function(){
 
    var win = Ti.UI.createWindow({
        title:'New Form',
        backgroundColor : 'white',
        orientationModes:[Ti.UI.PORTRAIT]
    });
 
    var label1 = Titanium.UI.createLabel({text: 'test label',});
 
    var txtDesc = Titanium.UI.createTextField({
        top: 37,
        style:Ti.UI.INPUT_BORDERSTYLE_NONE,
        value:'default',
    });
 
    var row = Ti.UI.createTableViewRow({height:'auto', hasChild: true});
 
    row.add(label1);
    row.add(txtDesc);
 
    var tableView = Ti.UI.createTableView({minRowHeight: 65});
 
    tableView.appendRow(row);
 
    win.add(tableView);
    return win;
}

Environment details: Titanium SDK version: 3.1.0.GA Built on: 17/05/2013 For: iOS 6.x, both simulator and device On: OSX 10.7.5 With: Titanium Studio, build: 3.0.2.201302191606