I just took a look, and it seems that the screen edge antialiasing is responsible for that 1 or 2 content-pixel reflection. For a quick fix, just change line 134 of shd_crt from this:
float width = max(1.0 / u_output_size.x, 1.0 / u_output_size.y) * 8.0;
Into this:
float width = max(1.0 / u_output_size.x, 1.0 / u_output_size.y) * 1.0;
Hope this helps! I'll most likely fix this in the download at some point in the near future.