ASM Requests

I said invisible and not targetable, not hidden: an hidden monster is not counted at all, that's why can't run won't work.
Btw, you cannot even assign can't run property to one monster of the formation? the other 100% working solution would be to duplicate one of the monsters of the formation and make it identical, with the only difference that the copy will have the can't run flag checked, finally you'll use the copy in that battle, rather than the original monster.
PS the copy won't be a waste of space in the monster list, since if you were ready to use an invisible monster, then you have one free slot for the copy

There could be another problem maybe: if the minions die, then you can run away... since the copy will appear just here, just add some line to the top of their code:

if var 0 >= 1 then
end if // the monster won't act anymore(dead)
.
.
.
// death check:
if monster is dead/hidden
make it appear with light and flashes*
add 1 to var 0 // if it's already used, use another var
monster becomes untargetable
end if

The monster won't fight anymore, it will seem dead and still ensure can't run property active.

* if the background(maybe one BG like esper bridge) will have a bad reaction to this like, then just assign to it the hidden status clear, instead.