Theres something knocking about which affects one wing and its not one of the usual suspects, para etc. I know of 3 fanciers in my club that have had 2 or 3 pigeons each go down with this. There's been no answers to what the problem is forthcoming, my guess is that its a bacterial infection....... but thats all it is...... a guess. It would be good to hear if others have encountered this problem and a diagnosis if they've had one.