After chaning mode to RTL, VTOL descends for approach

Hi guys.

We recently purchased a few VTOL and the supplier carried out test flights for each aircraft before shipping. Among those, one flight was hard to understand and I’ve tried to reproduce the flight with SITL but failed (actually, the result shown in the simulator was what I was expecting).

Parameter, Q_RTL_Mode, was set 0 but somehow the aircraft began to loiter down (just like loiter to alt cmd) on to certain preset altitude when the aircraft reached mission’s final WP in the actual flight.

There was messages like,

Mission complete, Changing mode to RTL
‘Descending’ for approach
Reached target altitude

after those events, the aircraft continued flying in the circle until it neared direct line to Home point.

What I was expecting was that when the aircraft reaches mission’s final WP, she fly directly towards homepoint and begin to loiter overhead.

Here are paramter and flight log.