I had a similar problem with one phone. Tested 3 different screens, all with the same result. When putting the original screen in or testing the screens in different phones all worked fine. I have been doing some iPad mini repairs lately and often as not if you have a ghost touch there, it is because you did not transfer all of the black tapes from the original screen to the new one. Parts of the screen will then make a connection with the aluminum frame and cause home buttons pressing themselves, ghost touch and loads of other problems.
On the iPhone 5 there should be a tape over the place where the backlight/lightbox cable is soldered to the connectors. You can see this in the green circle on the picture. If the tape is absent it looks like the on win the red circle. My hypothesis is that because the aluminum frames get bent a bit when falling, the absence of this tape does not always cause problems but sometimes does. I will let you guys know if I encounter the problem again in a phone and if its fixed with the tape. (I think the original tape is better then a regular scots/electric tape but can't remember the name of the specific tape kind so take it off your old screen for now)
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