Are you absolutely sure it's that? Unknown21 is usually just a pre-init animation, and Unknown128 is just a warp flash that uses the Dragoon's graphic to generate it with the standard warp flash iscript. I bet the problem is more likely the Dragoon's lack of a SpAbility2 animation. There is, however, a fairly easy solution for this:
Give the Dragoon a SpAbility2 animation. You could just copy-paste the attack script (bear in mind that Dragoons, like Marines and Ghosts, only use the GndAttkInit to set up the attack and the GndAttkRpt is where the action takes place) but replace the "attack25 x" command with
CODE
castspell
sigorder 2
Not too hard, see?
I seriously doubt that Unknown21 is causing the problem, as it's not used after the unit has finished appearing (nothing actually
calls it.) So try what I suggested and if it doesn't work, report it.
Note: Quite a few of the headers in ICECC's decompiles are mislabelled. Check out
This Topic for some coverage of what the actually do.