Mmh, Drop box might have derped and didn't uploaded the file correctly? Or I did that myself, who knows... In any case, I reuploaded the mod with the crash fix and another minor correction (I made a typo that prevented the faction from posting named bounties... I suppose I should have tested that more thoroughly)
As for the Swarmer, I does cause a small slowdown during launching, when the missiles seek their targets, but not so much during the flight. I didn't changed the code much so there shouldn't be any difference than before. If the lag is really unbearable, there isn't many ways to fix it but to reduce the number of missiles it launches (and that would be just sad
): 4 Swarmers means 200 missiles in flight at once, and their AI is already far simpler than the vanilla missiles. No amount of optimization will improve the performances if your processor is a bit old. I'll try to improve it a bit further but don't expect more than a couple of FPS.
Hm, now thinking of it, the adaptive Vsync of SS only allow 60 or 30 fps, so it is possible that when launching missiles, your fps goes slightly under 60fps and the game instantly cap it to 30, causing a much more noticeable difference than it should. Try disabling Vsync in SS/starsector-core/data/config/setting.json (line 8, right at the top) and see if it run more smoothly.