Bones & movement in Animate CC

When I create, say, 5 movieclip symbols, and link them all with a chain of bones, I can do basic IK.  But when I start moving things around the stage as I develop poses, inevitably the symbols "break free" of their bones, and end up all over the place.  I've tried a dozen different approaches, but I can't get the *&*#*$@ symbols to stick to their bones.  (This seems like a straightforward issue, but 99% of the tutorials I see keep their bone rigs static, so they never address this particular problem.)

What am I missing?

Thanks

g