SimpleButton's logic seems to fail in 3.5.3

I have a weird specific case scenario where SimpleButton’s will work in 3.4 but not in 3.5.3, i.e. the states don’t change as expected when hovering over and pressing the mouse down on the Neko target.

In the current state of my HaxeLive repository, I have a test for theme support using spritesheets. In my implementation, I am using the BitmapData.copyPixels call to create separate bitmap’s for each state as required. I realise this approach is slow, but it is the only method I could find that allows me to draw pixels without needing a Sprite or Tilemap. The code for this implementation is as follows:

private static function setupSpritesheet(style:Dynamic)
{
    if (style.type == "spritesheet")
    {
        if (__spritesheet == null)
            __spritesheet = Assets.getBitmapData(style.source);
        else
            return;
        
        var setup = Reflect.fields(style.setup);
        
        for (i in 0...setup.length)
        {
            var field:Dynamic = Reflect.field(style.setup, setup[i]);
            
            var data = new BitmapData(field.width, field.height);
            data.copyPixels(__spritesheet, new Rectangle(field.x, field.y, field.width, field.height), new Point(0, 0));
            
            __spritemap.set(setup[i], data);
        }
        
    }
}

The following JSON is being tested:

"ui": {
    "type": "spritesheet",
    "source": "img/light.png",
    "setup": {
        "Button": {
            "x": 0,
            "y": 0,
            "width": 128,
            "height": 32
        },
        "ButtonOver": {
            "x": 128,
            "y": 0,
            "width": 128,
            "height": 32
        },
        "ButtonDown": {
            "x": 0,
            "y": 32,
            "width": 128,
            "height": 32
        }
    }
}

And the image source being tested:

The results in OpenFL 3.4 is as expected, the cursor changes to the hand, and the logic functions as normal. However, in OpenFL 3.5.3, none of this happens.

Results (3.4):

Results (3.5.3):