I am new to the corny world, but absolutely in love with it. However, I am concerned about the small amount of beer that creeps into the gas line when I shake the keg during force carbonating. I have a ball/check valve b/w regulator and keg. However a small amount of beer still makes its way into the gas line. I haven't seen it make all the way to the regulator (gravity keeps down). I am curious if this is normal or do I need a new check valve?