I've been trying to use the bone tool in Animate CC 2017.
It's not very good.
There appears to be a fundamental problem with accuracy, which results in insane amounts of drift.
I guess this is because Flash works with space coordinates with a precision of 1/20 of a unit, but if you change the transformation point or translate a bone by holding alt, the rest of the armature points move slightly.
As an experiment try moving an element with the arrow keys, with each tick notice how the rest of the bones start moving about and ruining your armature?
This does terrible damage to an armature, often you can't even restore it with a series of undo operations.
Unless you think wild inaccuracy isn't a problem, I suggest you try and fix this.