beginning tutorials-How to Animate Cut out Puppet-Animateing the Hiker

Hi, this is my first post. While in the Harmony: the How to Animate a Cut out Puppet Tutorial, When I am adding Key frames to the timeline, and move the Character (hiker) arm to animate, then I watch the animation, I notice the arm of the hiker moves but the arm actually falls off the body and then moves. I’m wanting to animate it just like the instructor does in the video. Has anyone else ran into this? Does anyone know what mistake or mistakes I’m making?