Hi Kate,
Here is an updated version of the file.
https://drive.google.com/file/d/1BM6ymXQ_BAocxygNKfz6IHpjjISciak4/view?usp=sharing
I quickly scaled up and re-registered the symbols.
Potentially one of the problems is that they were created way too small. Even though Animate is vector-based it needs pixels and because of all the roundings, it is better to create characters larger.
Then there is an issue with little shakes. This is mostly fixed in Animate 20.0.3, so it will behave better in this regards.
Don't install it over your 19.2.1 though. Install separately because you might not like the changes.
The issue manifests itself at the end of tween spans when a symbol instance is a little skewed and a little rotated.
It is nearly non-existent in the attached file.
Hope it helps!
ps. Your work is amazing! You're very good and very talented! Wow!
pps. Still, check out the article on character rigging and grab a couple of the sample rigs that I've made.
http://flash-powertools.com/tag/free-download/
There are things that you can improve when you set up your characters for animation.
Nick - Character Designer and Animator, Flash user since 1998 | Member of the Flanimate Power Tools team - extensions for character animation