have you tried it without the image point moving every frame? that might have something to do with it. you can pin it in the position of the image point, but not actually to the image point (I think), so it won't follow a changing image point. Really can't help much without seeing it firsthand.. Maybe open a separate project with the minimal pieces and see if you can pinpoint the problem and if not, share with us the new project capx and we'll do our best!
I did remake the system on a blank file and the problem was solved. It must has to have something to do with the turret's constant changing of angle. The gun turns to face the direction you move into, so it's constantly rotating with a lerp effect. I've tried disabling as many conditions as possible but the problem just won't go away. I'll play around more today. Maybe there's something very obvious I'm just missing.
Perhaps you're positioning the arm before the events that move the body. You should put your events that position the arm after the events that move the body. If the events that move the body are after the arm events, then it will look like it is lagging because the arm would be positioning itself to the previous body position and not the current position.
I've tried putting the event to the very top and bottom of the event sheet but it's not changing.
This is just so weird because the arm keeps lagging behind and looks like I've added some kind of lerping to it even if I haven't. Setting the object's position on every tic should logically make it work, but there's something more technical going on that's causing this.