Hi... I have a two years old 580 EX ii... Over the weekend, I was taking pictures and when done, I tried taking it off the camera. Press the release button and normally, then I can slide it to the left to release it so that I can smoothly pull it out of the camera hot shoe. I pressed the button and then noticed that the lock release slider wasn't moving. Normally, I hold the camera on my right hand and then use the left hand to do it. I noticed a tension. I tried again... What? It wouldn't move. I then hold down the camera against the floor, left hand on the flash, right hand on pressing the release button. Still didn't move. After a while, I was able to get it off. I was confused. I put it away.
10 minutes later, my wife wanted additional pictures. I put it back on. Putting it goes fine. When done, I couldn't take it off again. I struggled with it after some times, and managed to take it off. That was on a 5D3.
Next day, I tried the flash on my 7D. Took two shots with it. Then tried taking it off. This was worse. It was like it was super glue onto my 7D. After numerous attempt, I got it off.
Anyone has experienced this behavior? Up unitl now, I have no issue with it and it performs flawlessly.