HTML5 canvas on iPad (with Phonegap) not working as expected - jquery-mobile

Question

I am developing an iPad application with Phonegap and jQuery mobile. One of the functions required is to allow the user of the app to sign (their signature) in 2 boxes. I am using easel.js to handle the "drawing" on the canvas element.
The HTML structure of this page is something like:
<div class="signature-wrapper sw1">
<canvas class="flexBox" id="myCanvas" width="240" height="240"></canvas>
</div>
<div class="signature-wrapper sw2">
<canvas class="flexBox" id="myCanvas2" width="240" height="240"></canvas>
</div>
Where the 2 canvas elements are where the signatures will be drawn. Below each of these elements are buttons to clear and save each of the elements. When clicked, they fire functions to clear the canvas, or save the canvas to an image (the image is then placed over the canvas, and removed on clear)
The save functionality looks something like:
function saveStage1(){
var canvas = document.getElementById("myCanvas");
var imageData = canvas.toDataURL("image/png");
$('.sw1').append("<img src='" + imageData +"' style='position: absolute; left: 0px; top: 0px;' />");
}
Basically, it is just getting the content of the canvas and saving it to a PNG image, which is then appended to the wrapper for the canvas elements. There is additional code I have left out of the code here for clarity, dealing with localStorage and db.transactions.
This function is working as expected.
The next function is to clear the canvas:
function clearStage1(){
oldMidX, oldMidY, oldX, oldY = null;
delete window.currentShape;
stage.clear();
stage.removeAllChildren();
stage.update();
var canvas = document.getElementById("myCanvas");
var context = canvas.getContext("2d");
var imageObj = new Image();
imageObj.onload = function() {
context.drawImage(imageObj, 0, 0);
};
imageObj.src = 'images/signature-client.png';
$('.sw1 img').remove();
}
This clears the canvas, nulls some variables, and recreates the canvas.
This works 100% in chrome and safari, but does not work correctly on iPad as a Phonegap application. On iPad, you can draw, but once you have clicked save or clear you are unable to draw without navigating away and back to the screen. It seems there is a JavaScript error somewhere on the page on both the save and clear functions which is preventing any further JavaScript from executing without "reloading" the page.
I have setup my console in Safari on mac to look at xcode application, and there is no error in the log. Any help would be appreciated.