Auto Focus sometimes stops while the subject is still out of focus, or subject tracking does not work properly.

Due to the characteristics of circular fisheye lenses, this lens produces strong distortion across the entire image.
Because of this distortion and depending on the shooting conditions and composition, Subject Recognition AF may mistakenly detect a subject in areas such as the background or sky and display an incorrect recognition frame.
As a result, AF may operate based on an incorrectly detected position and fail to focus properly (for example stopping with the focus far from the intended subject).
In addition, tracking may not work properly in areas with heavy vignetting or distortion around the edges of the image, so tracking may not start or may perform poorly.
In these cases, try AF again with the following settings:

• Turn off subject recognition priority in AF.
  AF menu → Subject Recognition → Subject Recog in AF → Off
• Turn off tracking.
  Set Focus Area to an item other than Tracking.