Assuming that your lure is not fresh out of the box and was functioning well before – in which case there is something wrong with the manufacture of the lure itself and should be exchanged – there are a few possibilities, the most likely of which is damage to the lure’s eyelet.
If your lure was caught on a hard obstacle recently, there is a chance that the eyelet may have become bent or jarred loose by the impact. Fighting a particularly strong or aggressive fish on the lure may also lead to the same kind of damage. In such situations, examine the eyelet and, with a pair of pliers, slowly bend the eyelet back so that it is once again perfectly perpendicular to the rest of the body.
As it is difficult to judge if your workmanship is perfect, here is a convenient way to determine where else the eyelet needs tuning. Cast the lure into the water and retrieve it. If it starts to swim to the left, the eyelet needs to be twisted more to the right; if it starts to swim to the right, the eyelet needs to be twisted more to the left. As such, it is best to do this sort of repair work right next to a body of water, where you may cast, retrieve, observe and tweak repeatedly as necessary.
Care should be exercised when tweaking the eyelet to not bend it too much in one direction. While it is unlikely that the eyelet will break off directly (unless you really use a lot of force), constant bending of the metal will quite naturally weaken it. Make many small tweaks rather than a single big one whenever possible.