Ok... I made a quick draft of what the problem is, so you can understand it better.
but in a few words, when I try to export an ai. file to PNG. (with transparent background)
For some reason it takes away 1 or 2 pixels (not in all the artboards)
It doesn't make sentence to me, they all should be exactly the same (except the words you will notice a difference in the PNG files I've attached)
Fingers crossed for some expert answers....
this is a nightmare since I am making thousands of illustrated files for different Android apps.
If you are using Clip to Artboard in the Images Size tab of Save for Web ... then first set your units of measure to pixels, click the Artboard tool and in the properties bar make sure that all of the artboard transforms x,y,w,h are even numbers.
If you are not using Clip to Artboard, Align to Pixel grid should avoid this problem and I see it is on your screenshot - just make sure it is on for all objects because it works on object level.