Those DC softparts are junk. A friend of mine ran LV5, and LV6 and both failed constantly, their turnaround time to send his parts was horrible, and the prices were over-the-top. I got a Sundown Zv2 kit in his LV5 (with an extra spider) and he thought it sounded better than OEM and it definitely held up to his abuse better.
First of all, at this point, you have nothing to lose by prying off the dustcap. Take a peak under there and you'll be able to see if the cone is separating from the spider there. If so you can just shim up the coil, dump the glue or epoxy of your choice in there, then reattach the dustcap and it should keep it going, if not you may find that the coil former is broken. If you bottomed out the sub hard you could have snapped the former. My friend broke a few formers.
Assuming that sub is older than a few weeks the coil will not be misaligned in the gap unless you have dropped the sub hard and shifted the pole piece. A coil misaligned from the factory would start rubbing within 4-5 hours of hard play.