I’m having a similar issue, but in the opposite direction…
When ‘end clip early if motion stops’ is switched ON, it nearly always ends prematurely, resulting in a video ending while there is clearly motion in the shot.
When I turn ‘end clip early…’ OFF, I get 20 second long clips recording back to back, recording absolutely no motion and just wasting my batteries.
Clips set to 20 seconds, 10 second retrigger time, sensitivity on max (had to do this after much experimentation), wifi signal is max. Batteries OK.
Last night the bloody thing recorded for 2 hours straight after being triggered by a fox at 6am. If I hadn’t disarmed the camera, it would still be recording now, probably.