I had a few cases like this one on almost all iphone versions.
If you are certain your problem is not the screen and you checked for obvious damage /loose parts near the lcd and touch fps connector then you might be facing this problem:
Your Touch IC itself or the solderballs under it are damaged causing this ghostlike action. This happens most of the time when a phone was dropped to often or to hard. The fact that you had to change the screen shows it had been dropped at least once. The solutions would be a replacement of that IC which is a bga repair and very difficult for beginner and needs alot of equipment.