In my present playtrough i didnt activate Conqueror, i.e. no settlement prebuilt and i ignored Jammer. At some point, as it happened to other people, Carla went berserkr in Sanctuary and started attacking Mama and then Sturges; Preston was my companion and he fighted Sturges too, the brothers were not in range to fight. When i attacked Sturges Preston left me so i reloaded, fast traveled to RR, summoned Carla with console and disabled her. Out of curiosity I tried enabling her and changing companion to Dogmeat; immediatly Preston started shooting with Carla. I reloaded again and makde a mental note not to send Preston to RR when i change partner. After some time having maxed Preston i switched to Piper that was in her office; when i left the office all Diamond city guards were shooting at poor Preston outiside Publik Occurrencies. With preston partner i went more than once in Diamond City without problems but Preston alone is seen as an enemy so it isnt a Carla problem but a Preston, and his group, one.