Horse has a different orientation of joints. It has x axis forward but NPCs in Darkmod have y forward. Different software have different conventions.
I re-exported the mesh, af.md5anim and walk_01.md5anim with y forward and x up orientations on head bone:
Vision cone is tied to it.
So I wonder if there's a way to correct cone's rotation independently from the head bone. Herbivores have close to 360 field of view, btw. Realistically there probably should be two cones.
Anyway, that doesn't change the erroneous behavior at 300 FPS.
In 2018 I also changed "tun_rate" from 150 to 41. Looks good for walking horse, and matches the turning animations, but it's too slow for running one. So when galloping, horses bump into walls and lose track of path nodes. Changing it back to 150 will fix that, but that's unrelated to super high frame rate bug.