Interesting. Full disclosure - the same lack of free time that makes FTSE development take longer also means that my latest playthrough is also stalled - my team has been waiting in Bunker Beta to start the Quincy mission since 2018. So I haven't really seen how the burst fix behaves in later missions.An issue I experienced during the Kansas City mission was that the burst weapon using SMs would not move closer. They would shoot from maximum distance, only hitting their pipe wielding SM allies and not making a real impact on the difficulty of that mission.
Is this possibly an issue with applying FTSE during a FT 1.27 campaign save, an unintended side effect of the burst fix, or something else?
I don't think it's the first point - FTSE doesn't (yet) persist anything in the save file, so I wouldn't expect there to be an issue with existing vs. new saves.
It likely is an unintended side effect. I don't think the AI itself should be impacted - from what I recall, the AI only used the regular chance-to-hit code when deciding what to do, so the FTSE override of the burst secondary hits shouldn't influence the AI decision making. My speculation (very unproven) is that it may be an issue of game balance for this mission - the playtesters would have done this mission with the original burst behavior in place, so the mutants may have always been firing from beyond their effective range, but because of the burst bug they may have been scoring more hits than they should have, so the difficulty may have seemed right. One way to determine this would be to play through the mission the same way with and without the FTSE (or original) burst bug fixes, and keep track of where the mutants are when they open fire. If they always fire from about the same range, but score more hits without the burst bug fixes, then this may be the explanation. If the mutants consistently fire from longer range with FTSE, then it probably is an effect of the burst fix on the AI, which I could then try to track down and tweak.