Customized Creature Sizes (tailmodels & invisible creature) Have No Walk Sounds + Spawn Animation Broken

I have a number of creatures customized to different sizes using the invisible no glow appearance with the tailmodel for the desired creature appearance. A prime example is different spider sizes. The ones modified this way have no footstep sounds; neither spiders nor beetles in this case do. Also, the spiders no longer do their "drop in" animation when they spawn, even though the dropin script is used. The spiders that haven't been changed still do the dropin properly.

They all animate properly otherwise, and have been matched to use the correct type (L, S, etc.) for their appearance.

Is there a way to fix the sounds and the animation?

If anyone is still looking for an answer for this...there isn't a fix since the footstep sounds and spawn-in animations would be part of the invisible creature model (and 2da entry) and not the tail model that is assigned to it.