XNA Deferred + Forward, Depth Problem?

Question

Im working with my deferred engine in XNA 4.0 and Im combining it with a forwardpipeline to support semi-transparency and other "forward only" effects.

Let me describe what I do:

1. Render GBuffer and all deferred geometry based on materials
2. A final composit where I combine the lightbuffer and the diffusebuffer from the GBuffer. I output color and depth to a rendertarget so I can use forward rendering to draw directly onto that RT.
3. Render forward geometry
4. I then take the RT from the forward pipeline and do postprocessing stuff.
5. Finally I write the RT to the backbuffer

Question:

• As you can see in the image below there's a problem with the boundingboxes. The are drawn using forward rendering and is drawn using the depthbuffer I descibed in step 2. I have tried to offset the depthbuffer in different directions with a texel or two. But nothing seems to solve the problem. Has anyone experienced this problem before?

EDIT: This post has been cleaned from some statements to avoid confusion.

Answer 1

Turns out, I was wrong. The source of the problem was in step 5 where I used a shader to copy the rendertarget to the backbuffer.

I forgot to correct the texture coordinates by negative texel X and Y. Not doing this results in incorrect sampling and color data being lost because the sample was taken at the wrong texel.