I watched the contractor install a bathtub so I could see how bathtub installation is done. Contractor drove some type of nail into each wall stud flush with the top of the flange of the tub. After the nail was driven in all the way it held down and fastened the tub to the stud.Then the bathtub area was tiled.Not long after installation I noticed the tub was loose and creeked when I was in it. The tub is loose.Is their a fix for this problem? Should the tub have been bolted to the studs by drilling holes through the flange and the stud then bolted? What can I do? I'm leaning towards removing the tub and installing a shower stall with a mason pan. Would a shower stall be better? Let me know what you think.