Bumping this, still no working mantis.
It seems that it might not be the conditionals after all. I originally arrived at the assumption that it was the conditionals because when I removed the conditionals and changed my sexps to only firing for one ship, they worked. I also individually tested each of the sexps I was using to see if it was specifically, for example, the set-afterburner or set-shield sexp that was giving me grief. It wasn't, so I made what I thought was a logical assumption that the conditionals were at fault. Maybe not so.
This time I went through and made individual sexps for each ship with lots of variables to tell it when to fire. After a lot of laborious sexping to comp[letely eliminate the conditionals I went back and tested only to find the same god damned bug. (You can't read it, but I smashed every single one of those last keystrokes. I am really frustrated about the whole thing). So I'm left with the possibility of either the every-time sexp not playing nice or the game not liking firing multiple instances of the same sexp for different ships. Or something else weird that I've not even thought of.
I'll experiment with it a little and post the results.