Make sure you aren’t trying to scale the bones when you animate them; Source Engine does not support bone scaling.
#Animation Neck stretches
proper python
naive elk
use the proportions trick
also make sure you have the right animations
make sure ur usin the male animations instead of the female ones or the npc ones
proper python
So how does the animation look in blender if it's correct as you say?
Its possible you may also be missing bones and Wilt simply doesn't modify bones that aren't present. Idk.
Since it looks like the spine is being placed downward among other things
Could also contact wilt's developer for help