Fail safe for potential loss of thrust in Px4

My friend’s quad drone crashed with his expensive camera while hovering at 60 Mtrs. He was using PX4. It was very stable as he was in pos_hold however suddenly he got potential thrust warning and quad came down. He shifted to land mode, but there was no response. PWM of all motors were at 1800 when the thrust loss warning came and the PWMs saturated for motors at 1950. actually the max pwm was also set for 1950. The RPM from his stick was only 62% when it was hovering at 60 Mtrs.

few questions are
can we setup any fail safe to ensure that the quad land safely in such conditions.
was the quad pushed to its limit at 1800 PWM? should or can we restrict quad reaching such stage by restricting height VIS-a-VIS load

You might get more help in the px4 forum: