Some of the twisting leg collars on my Gitzo tripodhave locked up, making it impossible to extend some sections. The tripod has never been abused, put into sand (except the last 2 inches of legs) and been stored inside for all it's life (four years) It has done a lot of travel in a motorhome ' inherently a lot of vibration. Short of using pump pliers, is there a good way to unlock them? I'm travelling in Mexico right now so a service location is very hard to find. I'm sure this is a common problem. Peter