Is it a front dinette? If so, the design of the table mount will always have some spring in it, like a diving board. We had a problem with ours because it kept slipping down as it was swung side to side. I kept tightening the knob to keep it at the height we wanted, but eventually I tightened it too much and did damage to the tubing, ending up with us having to get a new one on the warranty. When I got the new one, I went to Ace Hardware and bought two washers, one stainless steel one nylon, that fit the 1-1/2" tubing. I also bought a hose clamp that fit.
I installed the hose clamp, the stainless steel washer, and then the nylon washer on the down tube so that the nylon washer was making contact with the black plastic of the table mount. I tightened the hose clamp around the down tube at the height we desired to have the table. Now we don't need to tighten the black knob and the table swings side to side but does not lose elevation.