Seems that whatever I do These textures will always have a smudge or line on the corner, from what I see, it's 1 pixel wide. But I can't fix it. Suggestions?

the chest mapping is not 100% correct :P
if im not mistaken probrowser(?) is amazing with mapping ask him i guess

It's nothing you can do to fix it.
as kradox said, the mapping for the items is not correct.

I dont know anything about the mapping, but I guess you probably mean probowser, instead of browser.

He made my current set so you can dl/lp me if you want to check whether he's the person your talking about.

But probowser is a little bit inactive, since he's currently working on my new set but he hasn't been online for 1/2 weeks, yeah.

the texture must have an exact size of 128x128 / 256x256 or 512x512 and must have one color on the texture.

The template you find on forums isn't precise, there are 1 or 2 pixels of difference between the template and the effective texture. You should search for a different mapping to use, or try to fix it by yourself moving around the texture.

I fixed a part of it, the Top "SIDE" needs to be one pixel layer taller (Past the bottom "SIDE" box) according to that rule, to fix the other side the pixel layer would have to go below the bottom of the bottom "SIDE" box (Making the picture technically 128x129, but then again, I lack the patience to try all combinations so I may be wrong.) This may be confusing so I will include a picture
-----
Here.