The adjustable drain barrel in my tile shower has become slightly loose. Wobbles back and forth slightly. There is a slight gap around the drain and tile grout. The drain flange and pipe seem to be securely fastened and do not move at all. The shower is a custom mortar bed job. What is the best way to secure this loose portion of the drain and make it watertight so the water goes down the drain and not around the drain? Why did this part of the drain become loose to start with? The shower was installed about 3 years ago.