That makes more sense if it's just the fight with Sword Dance and Hammerblaster; the default game has no encounter where these enemies appear together. There's two ways you can fix it on your end; if you can use Proud Clod, you could go into the scene.bin, find scene 107, and go into it's Formation data and change formation 01AC so that Hammerblaster doesn't appear (you'd be changing all the numbers in the rows belonging to 0035 and 0036 to FFFF; that should get rid of him).
Otherwise, you can try doing it using the field editor Makou Reactor. Open the flevel with it and go to field 248 (called blin65_1). Under the Tools tab (or by pressing Ctrl+N) you can edit the encounters found on that field. Battle 5 (428, with a probability of 10) is the fight with the Hammerblaster + 2 Sword-dances. Change that to any of the others, 424, 425, etc. and that should make the battle never appear. If Makou can't save the changes, then try moving the flevel out of the program files/steam folder and then editing it before putting it back where you found it.
As for the actual cause, I'll bet it's to do with the Var: 0000, 0020, and 0040 that both Hammerblaster and Sword Dance use in their pre-battle. Might be that Hammerblaster is trying to store formation data to synch with his No-Name part and it's being scrambled by Sword Dance using the variable for something else. I'm not an AI expert but I've had trouble with things like that in the past.