Replacement screen having "fogging" issues.

Have replaced multiple screens and every now and then come across this odd effect that's almost fog like. It starts with a thick white color along the border that gets lighter as it works its way into the center, where the image is flawless. Some thoughts of whether they are cheap defective screens, moisture issues, or just maybe something not put together right the first time causing pressure points around the edges. Just curious if anyone has any thoughts on this or have run into this as well.