jumpy screen, is fine and then isn't. Very temperamental

Heyy! So I did a DIY on my brothers old IPhone which was majorly beaten up, I think he fell out with it when he was drunk.

Anyway I replaced the screen once, and it was unusable - touch screen jumping and going mental 24/7. So I took it apart and cleaned it all, then put it back together and the same. So I sent the screen back and got a new one.

Same issues, but not as bad. Very temperamental, one minute it is beautiful. And when I use it for prolonged periods of time it starts to go mental again.

Ive also noticed that using one of those touch screen pens works really well and eliminates ALOMST all of the problems. So I'm thinking it could be to due with static, and the moisture on my hands. If anyone has any ideas before I DIY further and probably break it then please let me know. Thank you for reading!!!

Seamus.