I have two Blum Servo Drive hands free trash pull outs. They were both installed by our cabinet maker. One works great slight touch and garbage cans kick out all the way. The other one we had a lot of problems with just opening the trash can. Sometimes it would work or we had to push hard. It also only kicks the garbage cans out half way. The cabinet people came out and looked at it and first said it was the bumpers but we have the bumpers in place looks exactly like the other trash can . You can also hear the difference when the Servo Drive opens the garbage, One sounds much stronger than the other. Any suggestions? I feel like we got a dud but they are insisting that it is good. Have been using for several months and for the price the two are like night and day in performance. Any advice would be much appreciated!