central locking on y reg corsa?

when i use the fob to open doors,the drivers catch and the one behind it jump up and down the other sides two door catches do nothing. by using the key in the lock i can with one turn open drivers door then with two turns assess all doors. if i leave drivers door open the catch on that does not work but all the others then work as normal . think i felt something grind the other day as i opened drivers door ? and it seems since then the problem started ? doing my head in please help !