STEERING MODE - curved path

I’m pointing the rover in a particular heading and sometimes I see the rover taking a curved trajectory and sometimes I don’t .

I am using the latest ardu rover code from master.

I’m not quite sure how to set a heading and what I’m suppose to see in mission planner.
How come I don’t see the target heading (green line) in steering mode.

What is the orange line representing and how come I can’t change the heading of the orange line no matter what I do with the rc transmitter stick.

I am currently using the 3dr GPS/ Mag combo (calibrated)…even though the arrow on the module is pointing in the same forward direction as my platform … I needed to put a roll180 offset otherwise I get an ekf variance error.