Ugh, that is one of them there new fangled crank/bottom bracket. I think the drive side (right) crank arm is one piece with the hollow shaft that goes through the bearing cups that are screwed into each side of the bottom bracket shell. The non-drive side (left) end of the shaft has splines at the last inch and a threaded hole on the end. The non-drive side crank arm fits on to the splines and an Allen bolt tightens into the hole. So there is only one bolt holding the crank together and to the bottom bracket.
I'd check if the Allen nut is tight. Otherwise, it is possible one or both cups are loose, but they require a special tool to tighten/loosen, or the bearings could be worn out.
See
Park Tool Co. » ParkTool Blog » External Bearing Crank Systems (Hollowtech II, MegaeXo, Giga X Pipe, X-type, Campagnolo Ultra Torque)