XBOX 360 controller LB button?

And my question refers to the LB button of my 360 controller. Very often I have to press this very firm for a reaction to take place. But that's funny. Blow me hard once the LB button and zeische. Responds normally for a short time. Did the controller synonymous open because I ran out of dust. NOTHING. There's nothing stuck or similar. The press is quite normal only the reaction more often. After the puffing it goes back to normal for a short time. Whatever one is possibly wrong with the button?

He is just in arrest.