Every missile that can be controlled manually (Titan AP, Scalpel,...) will freak out at range around 4000m as shown on the video. Config reference tells that maxControlRange sets the maximum range of control but Scalpel (shown on the video) has maxControlRange = 11000. So two things are wrong

• the maximum range seems to be hardcoded to around 4000m, config value doesn't matter
• rocket should fly straight after that and not fly in circles trying to hit imaginary point on a 4000m radius sphere.

With the second problem there is connected another one - missile will always fly either to the point on the ground under cursor or the point on a 4000m sphere if aiming at something at the sky. This means it might be difficult to hit a vehicle that is skylined (only sky behind it) because missile will fly well past beyond the vehicle to the point on the 4000m sphere. Missiles should intercept aiming point immediately. All of this also applies to Titan AP, it's not UAV exclusive.
See the video here, it shows the missile in live action: https://www.youtube.com/watch?v=7L0opyOiGr8
It also proves that Scalpel has enough range when using laser designated mode.