Unfortunately both of my Tapo c520ws camera's do not return to its original position after motion tracking. 

What I did to try to solve it:

1. disabled motion tracking, reboot the camera, set the camera to the desired position, enabled motion tracking
2. pan/tilt correction
3. set detection zones, remove detection zones
4. changed default position

What else can I do? Reading om the forum the problem occurs on almost all camera's.