Chosen Solution
Not sure whats going on, iPad Mini 2 Retina: Tried different screens from different suppliers, and it still happens. It’s an original smart cover, yet the problem still occurs? Magnets are in place properly, and all the screws, connections and what not are in the original place. Answers :)!? Cheers.
I suspect you have an issue with the Hall sensor on your replacement screens. Check out this answer (iPad Mini Wake Magnet Sensor), it should help you out.
