There's a difference between "dropping" and "alignment." From your description, I'm not sure which one you're talking about. Dropping means that your bow arm drops when you shoot the bow, i.e. poor followthrough. Poor alignment means that you're not maintaining the proper "T" shape of your arms and shoulders as you hold the bow at anchor.
Alignment problems are common if most of the time we're shooting at a target lower to the ground than the tip of our arrow, so we get lazy and point our bow arm down at the target, rather than tilt at the waist to maintain the good "T" configuration. That's why blank bales are usually set up so that you can shoot horizontally into the bale, which automatically gives you the good "T" alignment of your bow arms and shoulders. You should maintain that same "T" when you shoot down or up by either tilting at the waist or bending a knee if the angle is more extreme.
Dropping, on the other hand, is an instantaneous reaction to the shot. I don't really know how to cure it, other than just making sure that I continue holding my bow up in the shooting position until my arrow hits the target.