Like Brian said, it is most likely the digitizer cable getting bunched up between your frame and digitizer. Try pulling it towards the LCD with a pry tool while laying the screen down.
I really came to answer about your better seal for iPad adhesive though. There is a certain process we use here at the shop to ensure the best, and longest lasting seal possible. There's nothing I hate more than to have a customer bring back an iPad thats lifting along the digitizer, looks very unprofessional. So what we do is remove the old screen and LCD, then use scotch-brite or some some other metal sanding material, and soak it with 99% iso and then use it to scrub away all traces of old adhesive. It also tends to roughen up the aluminum mounting surface so adhesive sticks a bit better. Once all old adhesive is gone, we use this : http://www.tesatape.com/industry/buildin.... Just lay long pieces of tape around the edges and use an x-acto knife to custom cut it. Leave no gaps. Then after reassembly, we use multiple wood clamps around the edge of the iPad and heat it up with a heat gun several times while it's under pressure. After about 30 minutes with the clamps on it, its good to go. We have not had one single iPad come back after using this method. Hope it helps!