I have an issue with some corner beads. I have a short area (approx. 5" x 6" X 81") that I have beaded and the bead is flared out (it didn't look that flared when I installed it. So now the panel is concave.
The way I look at it I can either fill in the area with mud or un-install the bead and try to re-seat (PITA).
You can get a bead clinching tool at home depot that comes with a rubber mallet. The tool sits over the corner bead and when you strike it with the mallet, it seats the bead and puts a couple of notches in the bead to hold it to the drywall. You still need to secure the bead. I like using drywall nails for this. The tool isn't very expensive and is actually fun to use.
If you don't want to go that route, use some dry mix mud to fill in the recess. One of the easisand products would work well, 45 or 90.