Here is a man I created. I thought I did the skeleton/bone creation correctly, however whenever I move the upper leg bone, the lower leg (child bone) moves, but the shape (upper leg) disappears or goes somewhere off screen…I don’t know.
I wanted the attach the file here to help solve this but apparently new users aren’t allowed to attach files.
Hello.
Could you check this video below?
Pay attention at 0:20 to what handle you should link to bone.
Yes, I am well past that point. I have several bones/child bones connected.
To use your video example. If I were to use the blue handle to move the bone, the image would actually disappear. Ctrl Z brings everything back to where it belongs.
That is the question…when I move the bone, the image (or shape) disappears.
I have solved my issue. To summarize, you can’t join a bone directly to a shape. The shape must be placed in a folder. Then the bone and folder are linked without issues.
Orginally, the shape center point was so far off the shape itself that when the bone did a rotate, the shape rotated right off the screen.
Please check the (good old) Wiki to find all the answers about bones 
https://wiki.synfig.org/Doc:Basic_Bone_Tutorial