To clarify I'm talking about a lane change initiated by me rather than merely allowing one recommended by the car. The latter only requires a brief flick of the turn signal stalk.

But the former required me to actively hold it down for several seconds--much longer than a full turn signal would require. I had to hold it down until the car was completely within the stripes of the adjacent lane or the car would immediately swerve back into the original lane. I tested it many times on a traffic-free road. Might have been a setting; I don't know.