Why won't my iPod screen stay in all the way?

From my experience, the metal plate at the top of the screen is put back on, it never works again once its removed from the screen. If thats on there, then thats your problem, if its not, then its just the poor adhesive they use. Ive had this problem in my store when I fix ipods. I found out the solution is to take super glue and put a DAB on each corner and put small clamps on the corners to hold it down. If theres pressure on the LCD, thats probably because they didn't secure the metal plate underneath all the way down.

This is a common issue with the 4th Gen iPod replacements. Basically, all that is holding the screen on is double sided tape, and a very thin strip of it. There are a bunch of methods to help get it to sit right and stay, but it is a crap-shoot, and just bad planning and design in the first place. Fortunately, the later Apple mobile devices use screws instead of adhesives.