Problems with touch screen

Hello you guys,

i have some troubles with an iphone 6s screen, i wanted to know what i might did something wrong here,

i buyed a iphone 6s screen and i assembly all the parts together, i put my screen in to place and HURRAY it works, but after a few minutes when i was working on it , i start to notice there is a scroll problem and also when swiping its some times stuck. i reopend my iphone to make sure the connector was propperly clicked in,i try to use my cracked screen and there i did not have any problems, and when i place the new one in aggain its back from the start

can you damage a componment on the lcd screen when placing the heat shield on?

or is an faulty screen , because i dont have any pixel dots or any other problems with 3D touch etc,...

Thanks for replying!