Your log doesn't show anything bad, the error was just an interruption when downloading.
You can upload a screen recording to a site like YouTube or Google drive.
Ideally you could provide 1) your project file (usually we don't need the images), and 2) the steps we need to take to see the problem. That's much better than a video because with a video we have to try to recreate the situation by watching the video, which is hard and not always possible without your project file. If you need to email us files you can use: contact@esotericsoftware.com
The bug you found sounds bad, so we'd be very happy to fix it!
Thanks for the project file. What is happening is that you have set scale Y to zero in the setup pose. Animation values are relative to the setup pose values. For scale, the scale you set in an animation is multiplied by the setup scale. When your setup scale is zero, any value you set in an animation is also zero.
What you can do instead is to leave the scale as 1 in the setup pose and then key the scale to 0 as needed in your animation.
However, a scale of zero is still going to play havoc with math throughout your skeleton. That is why you can't move vertices of the meshes that are bound to the bones with zero scale. What you can do instead is use a scale like 0.0001. That likely will look the same to you, but makes a BIG difference for the math.
A scale of zero creates a singularity and can be a bit of a surprising special case. We don't want to disallow it since it may be useful sometimes, but it does make for an unexpected gotcha. What we can do is add a warning if zero scale is used on a bone in the setup pose.
