http://web.canon.jp/imaging/eosd/firm-e/eos1dm4/firmware.html
This firmware update (Version 1.0.6) incorporates the following enhancement.

Firmware Version 1.0.6 enhances the AF tracking performance.*
*AF performance has been enhances for receding subjects and for subjects that are approaching at a low speed.

提高了AF精度，提高了低速靠近物体的精度

解决的速度还是蛮快的