Digitizer/Screen keeps popping up after replaced? any help?

I have replaced the screen/digitizer on probably 5 or 6 ipad 2's and on every single one i have replace the most difficult thing is to keep the screen/digitizer glued down, it keeps popping up in one problem area on every IPAD. I have used the adhesive that the new screens come with, i have also tried buying different adhesive and still get the same issue. I make sure the frame is cleaned of any and all old adhesive and i make sure that the frame isn't obstructing the new screen from laying flush. So far i cannot find any answer and i dont understand why im having such a hard time with this issue. Every video i watch never puts much information into this problem and always act as if you just place it down in the right place and it always stays. Any help would be very greatly appreciated. I am finding myself straying away from IPAD repairs because of this issue and if anyone has any answers it would be greatly appreciated. thx