Chosen Solution
I just recently replaced the back glass for my S8 because the old one was cracked. However, the new glass isn’t fully adhering to the frame. After applying pressure, a small gap remains on the long sides between the back glass and the phone. How can I make sure the back glass fully sticks?
did you cleaned and replaced the adhesive too? Galaxy S8 Rear Cover Adhesive
It could be low quality adhesive. I recommend using 3mm adhesive, not the premade stuff. I also recommend to put a soft rag over the phone and leave about 10 to 15 pounds of weight on top of the phone for about 2 hours. I use 3 five pound weights that were previously used for dumbells. Hope this helps.