Smart forfour Bj2017 Central locking problem

Hello, I have a problem with my wife’s car, and he does the following : when I open the central lock with the key, this problem goes without problem when I get out of the car again and try to close the car Unfortunately, the connection and unlocking does not work anymore or only sporadically. There is always a clapping but no locking. I noticed now that the key also partly reacts very sensitively even if I just stroke over it, he tries to unlock or lock what only succeeds once in a while. Sometimes the key only works when I move it or shake it, start it and drive it easily. Have already checked all doors, switch key battery, disconnected vehicle battery from time to time. Here is a video of the situation.