If you separate the two pieces and organise a circular joint it probably will work as intended.
But generally it does not seem worth spending any time with bones in Animate.
Their implementation will constantly give you frustrations and the way the armature layers are designed will prevent you from comfortably timing your animation.
it's been some time since I last used the tool, it seen simple and something the Adobe could already have fixed.
Since we are talking, I'm anxious to see how EDAP 5.0 will look like!
I don't think they have touched the bones/armature at all recently.
v.5 is coming very very soon
Hope you're well!