Just in case anyone else is having trouble spotting the difference, I've made a little diagram. Basically there should be a gap (i.e. shadow) all the way across the magnets, not just on the ends.
However, while it's not as reliable, I think you should be able to check if your drivers are stuck without taking the grilles off. If you shine a very bright flashlight from the grille side and look in the earpad you should be able to see light coming through the membrane. It (confusingly) shines blueish where it's gold coated (in between the magnets), and yellow where the coating is different (directly under the magnet bars). by moving the light back and looking at it from different angles you should be able to see alternating colors. View it straight on looks basically all blue, and at an angle it should shine mostly yellow.
Although I can't confirm this since my set is healthy, but if it's stuck, I would theorize you could only see the blue light in the middle where it sticks, even when viewing at an angle since the magnets would be blocking the light. I took a picture, but it's kinda hard to make out both colors, but it's way easier to see in real life as long as you have a really bright flashlight. And, the best part is that poses no more risk to the headphone than normal handling requires.
Anyway, I hope that's helpful to you (or anyone, for that matter) and I hope these stuck drivers are sorted out! I consider myself lucky that my set has been trouble free, even after hundreds of hours that I've put on it since I bought it.
