Animation Export Problems

Essentially a repost of my topic at blender stack exchange.
My problem is that my animation displays incorrectly after I export from blender. I’m using rigify and “export only deform bones”. The problem seems to be with the scale of some bones, which is being modified, causing strech problem, mostly on my creature’s legs. This problem has happened many times for me and despite reading the blender docs and many threads, I saw no mention nor solution to this problem. The link above has more info.
blend file:

As an update on this, I’ve managed to make it passable by using an addon to generate a second rig and baked an animation to it, then exported that rig with just the deform bones. That is very much what “only deform bones” option should be doing, but apparently, those two things are different. Still looking for an “ideal” workflow on this.
More info on that can be found at The addon in question is by angavrilov.

HI, changing the bones Volume Variation to volume-None or influence to zero, sims to fix it.