If your chuck is wobbling first check to see if the chuck is loose, if so tighten it by turning it clockwise. If that isn't the issue than the threads that allow the chuck to tighten may be caked with build up not allowing the chuck to fully tighten, to fix this remove the chuck and clear any build up. If that does not fix the wobbling issue either than your chuck is most likely defective it is advised you purchase and install a new one.