Z-Depth resetting, why?

[Majicpanda]

I've got the following structure:
-Panel
-- Anchor
--- Panel (Draggable)
---- UI_Grid
----- Artwork (GO with drag panel contents) and data for each artwork piece
------ Purchase Button Widget
------ Label (Cost)
------ Label (Name)
------ Background (UISprite)
------ Image (UISprite)

Background and Image are on 2 different atlases so I've adjusted Image to have a Z of -.1 to offset it towards the camera.  The problem is, when I start my game the Z gets changed to 0 by something.  Do you know what's causing this reset based on my hierarchy? Disabling UIGrid doesn't fix the problem, so I have no idea why it's changing my Z depth of the GameObject.

Here's some info that might help.. in Start I'm doing the following:
_sprite.spriteName = "Lock";
_sprite.MakePixelPerfect();

I removed these 2 lines and the Z doesn't get changed from what I want it to.

[Majicpanda]

I fixed this by setting my z depth to -1... I found the following in UISprite:   

1. // Sliced sprite should have dimensions divisible by 2 for best results
2. Vector3 pos = cachedTransform.localPosition;
3. pos.x = Mathf.RoundToInt(pos.x);
4. pos.y = Mathf.RoundToInt(pos.y);
5. pos.z = Mathf.RoundToInt(pos.z);
6. cachedTransform.localPosition = pos;

So you have to be careful when using Z position and use whole numbers only.

[freeglass]

NGUI Depth Manager you requested issues can be fixed by using.

This program is a tool designed to help solve problems that occur while using NGUI Widgets Depth .

NGUI Depth Manager in AssetStore