Looks like you replaced the Fenris' Standard Command section with a Hammerhead Command section. Those typically increase maneuverability, not decrease it.
i thought they reduced manoeuvrability but increased the number of weapons you can mount on the command section
Nope, the Hammerhead adds guns, armor, and additional maneuvering thrusters. There's no excuse to use anything but one of those on combat ships once you get Waldoes and until you get Battlebridges.