AMSL navigation negative relative altitude

I work in a Python application that we need to follow the terrain and, in some cases, under the altitude level of the home.

The problem is that, with the SITL simulator, when the drone reaches relative level 0 it stops during the route.

I have verified that, in the home is annotated the AMSL height, the route data is in AMSL (GLOBAL), and I tried the different ways of sending the drone to a point.

Any idea of configuration or solution to fly in negative relative?

TKANKS!!!