I just noticed something and wonder?
You have some shadow going on the frames and it appears from the screenshot the shadows are only on the corners?Am I correct?
If so, this is throwing off your frames. The space , even if you cannot see anything there, allotted for the shadows has to match with the side frames.
So, if your shadow extends 3 pixels past your top frame side edges, you need to add 3 pixels of space to the side frame canvas.
Hope that makes sense.
If you are using stock shadows, which it does not appear, but if so, something is wacked bid time.
Luck.