My problem is kinda similar but it's not the exact same. I changed my screen over a month ago because I droped my Ipad mini on the floor and completely shatered the screen. Since I repaired it on my own there had been no problems but now that ghost thing happens. It stills picks up where I touch it but it mostly does what I assume is double taps at random since it keeps opening pictures and zooming on them. It also opens apps at random but it doesn't do anything crazy like writing on its own. It mostly happens when I type on the keyboard but the ghost is now too annoying for me to ignore it. I'm slightly scared of reopening the screen like everyone else do because I don't think I have the tools anymore and it's too much of a presise job for me. I curently don't have any protection on the screen but I think I droped a screw in when I changed my screen so that might be the cause of my trouble.
Any help or tip is greatly appreciated.